diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-includes/blocks.php
--- a/wp/wp-includes/blocks.php	Thu Sep 29 08:06:27 2022 +0200
+++ b/wp/wp-includes/blocks.php	Fri Sep 05 18:40:08 2025 +0200
@@ -17,14 +17,14 @@
  */
 function remove_block_asset_path_prefix( $asset_handle_or_path ) {
 	$path_prefix = 'file:';
-	if ( 0 !== strpos( $asset_handle_or_path, $path_prefix ) ) {
+	if ( ! str_starts_with( $asset_handle_or_path, $path_prefix ) ) {
 		return $asset_handle_or_path;
 	}
 	$path = substr(
 		$asset_handle_or_path,
 		strlen( $path_prefix )
 	);
-	if ( strpos( $path, './' ) === 0 ) {
+	if ( str_starts_with( $path, './' ) ) {
 		$path = substr( $path, 2 );
 	}
 	return $path;
@@ -35,98 +35,222 @@
  * and the field name provided.
  *
  * @since 5.5.0
+ * @since 6.1.0 Added `$index` parameter.
+ * @since 6.5.0 Added support for `viewScriptModule` field.
  *
  * @param string $block_name Name of the block.
  * @param string $field_name Name of the metadata field.
+ * @param int    $index      Optional. Index of the asset when multiple items passed.
+ *                           Default 0.
  * @return string Generated asset name for the block's field.
  */
-function generate_block_asset_handle( $block_name, $field_name ) {
-	if ( 0 === strpos( $block_name, 'core/' ) ) {
+function generate_block_asset_handle( $block_name, $field_name, $index = 0 ) {
+	if ( str_starts_with( $block_name, 'core/' ) ) {
 		$asset_handle = str_replace( 'core/', 'wp-block-', $block_name );
-		if ( 0 === strpos( $field_name, 'editor' ) ) {
+		if ( str_starts_with( $field_name, 'editor' ) ) {
 			$asset_handle .= '-editor';
 		}
-		if ( 0 === strpos( $field_name, 'view' ) ) {
+		if ( str_starts_with( $field_name, 'view' ) ) {
 			$asset_handle .= '-view';
 		}
+		if ( str_ends_with( strtolower( $field_name ), 'scriptmodule' ) ) {
+			$asset_handle .= '-script-module';
+		}
+		if ( $index > 0 ) {
+			$asset_handle .= '-' . ( $index + 1 );
+		}
 		return $asset_handle;
 	}
 
 	$field_mappings = array(
-		'editorScript' => 'editor-script',
-		'script'       => 'script',
-		'viewScript'   => 'view-script',
-		'editorStyle'  => 'editor-style',
-		'style'        => 'style',
+		'editorScript'     => 'editor-script',
+		'editorStyle'      => 'editor-style',
+		'script'           => 'script',
+		'style'            => 'style',
+		'viewScript'       => 'view-script',
+		'viewScriptModule' => 'view-script-module',
+		'viewStyle'        => 'view-style',
 	);
-	return str_replace( '/', '-', $block_name ) .
+	$asset_handle   = str_replace( '/', '-', $block_name ) .
 		'-' . $field_mappings[ $field_name ];
+	if ( $index > 0 ) {
+		$asset_handle .= '-' . ( $index + 1 );
+	}
+	return $asset_handle;
+}
+
+/**
+ * Gets the URL to a block asset.
+ *
+ * @since 6.4.0
+ *
+ * @param string $path A normalized path to a block asset.
+ * @return string|false The URL to the block asset or false on failure.
+ */
+function get_block_asset_url( $path ) {
+	if ( empty( $path ) ) {
+		return false;
+	}
+
+	// Path needs to be normalized to work in Windows env.
+	static $wpinc_path_norm = '';
+	if ( ! $wpinc_path_norm ) {
+		$wpinc_path_norm = wp_normalize_path( realpath( ABSPATH . WPINC ) );
+	}
+
+	if ( str_starts_with( $path, $wpinc_path_norm ) ) {
+		return includes_url( str_replace( $wpinc_path_norm, '', $path ) );
+	}
+
+	static $template_paths_norm = array();
+
+	$template = get_template();
+	if ( ! isset( $template_paths_norm[ $template ] ) ) {
+		$template_paths_norm[ $template ] = wp_normalize_path( realpath( get_template_directory() ) );
+	}
+
+	if ( str_starts_with( $path, trailingslashit( $template_paths_norm[ $template ] ) ) ) {
+		return get_theme_file_uri( str_replace( $template_paths_norm[ $template ], '', $path ) );
+	}
+
+	if ( is_child_theme() ) {
+		$stylesheet = get_stylesheet();
+		if ( ! isset( $template_paths_norm[ $stylesheet ] ) ) {
+			$template_paths_norm[ $stylesheet ] = wp_normalize_path( realpath( get_stylesheet_directory() ) );
+		}
+
+		if ( str_starts_with( $path, trailingslashit( $template_paths_norm[ $stylesheet ] ) ) ) {
+			return get_theme_file_uri( str_replace( $template_paths_norm[ $stylesheet ], '', $path ) );
+		}
+	}
+
+	return plugins_url( basename( $path ), $path );
+}
+
+/**
+ * Finds a script module ID for the selected block metadata field. It detects
+ * when a path to file was provided and optionally finds a corresponding asset
+ * file with details necessary to register the script module under with an
+ * automatically generated module ID. It returns unprocessed script module
+ * ID otherwise.
+ *
+ * @since 6.5.0
+ *
+ * @param array  $metadata   Block metadata.
+ * @param string $field_name Field name to pick from metadata.
+ * @param int    $index      Optional. Index of the script module ID to register when multiple
+ *                           items passed. Default 0.
+ * @return string|false Script module ID or false on failure.
+ */
+function register_block_script_module_id( $metadata, $field_name, $index = 0 ) {
+	if ( empty( $metadata[ $field_name ] ) ) {
+		return false;
+	}
+
+	$module_id = $metadata[ $field_name ];
+	if ( is_array( $module_id ) ) {
+		if ( empty( $module_id[ $index ] ) ) {
+			return false;
+		}
+		$module_id = $module_id[ $index ];
+	}
+
+	$module_path = remove_block_asset_path_prefix( $module_id );
+	if ( $module_id === $module_path ) {
+		return $module_id;
+	}
+
+	$path                  = dirname( $metadata['file'] );
+	$module_asset_raw_path = $path . '/' . substr_replace( $module_path, '.asset.php', - strlen( '.js' ) );
+	$module_id             = generate_block_asset_handle( $metadata['name'], $field_name, $index );
+	$module_asset_path     = wp_normalize_path(
+		realpath( $module_asset_raw_path )
+	);
+
+	$module_path_norm = wp_normalize_path( realpath( $path . '/' . $module_path ) );
+	$module_uri       = get_block_asset_url( $module_path_norm );
+
+	$module_asset        = ! empty( $module_asset_path ) ? require $module_asset_path : array();
+	$module_dependencies = isset( $module_asset['dependencies'] ) ? $module_asset['dependencies'] : array();
+	$block_version       = isset( $metadata['version'] ) ? $metadata['version'] : false;
+	$module_version      = isset( $module_asset['version'] ) ? $module_asset['version'] : $block_version;
+
+	wp_register_script_module(
+		$module_id,
+		$module_uri,
+		$module_dependencies,
+		$module_version
+	);
+
+	return $module_id;
 }
 
 /**
  * Finds a script handle for the selected block metadata field. It detects
- * when a path to file was provided and finds a corresponding asset file
- * with details necessary to register the script under automatically
+ * when a path to file was provided and optionally finds a corresponding asset
+ * file with details necessary to register the script under automatically
  * generated handle name. It returns unprocessed script handle otherwise.
  *
  * @since 5.5.0
+ * @since 6.1.0 Added `$index` parameter.
+ * @since 6.5.0 The asset file is optional. Added script handle support in the asset file.
  *
  * @param array  $metadata   Block metadata.
  * @param string $field_name Field name to pick from metadata.
+ * @param int    $index      Optional. Index of the script to register when multiple items passed.
+ *                           Default 0.
  * @return string|false Script handle provided directly or created through
  *                      script's registration, or false on failure.
  */
-function register_block_script_handle( $metadata, $field_name ) {
+function register_block_script_handle( $metadata, $field_name, $index = 0 ) {
 	if ( empty( $metadata[ $field_name ] ) ) {
 		return false;
 	}
-	$script_handle = $metadata[ $field_name ];
-	$script_path   = remove_block_asset_path_prefix( $metadata[ $field_name ] );
-	if ( $script_handle === $script_path ) {
+
+	$script_handle_or_path = $metadata[ $field_name ];
+	if ( is_array( $script_handle_or_path ) ) {
+		if ( empty( $script_handle_or_path[ $index ] ) ) {
+			return false;
+		}
+		$script_handle_or_path = $script_handle_or_path[ $index ];
+	}
+
+	$script_path = remove_block_asset_path_prefix( $script_handle_or_path );
+	if ( $script_handle_or_path === $script_path ) {
+		return $script_handle_or_path;
+	}
+
+	$path                  = dirname( $metadata['file'] );
+	$script_asset_raw_path = $path . '/' . substr_replace( $script_path, '.asset.php', - strlen( '.js' ) );
+	$script_asset_path     = wp_normalize_path(
+		realpath( $script_asset_raw_path )
+	);
+
+	// Asset file for blocks is optional. See https://core.trac.wordpress.org/ticket/60460.
+	$script_asset  = ! empty( $script_asset_path ) ? require $script_asset_path : array();
+	$script_handle = isset( $script_asset['handle'] ) ?
+		$script_asset['handle'] :
+		generate_block_asset_handle( $metadata['name'], $field_name, $index );
+	if ( wp_script_is( $script_handle, 'registered' ) ) {
 		return $script_handle;
 	}
 
-	$script_handle     = generate_block_asset_handle( $metadata['name'], $field_name );
-	$script_asset_path = wp_normalize_path(
-		realpath(
-			dirname( $metadata['file'] ) . '/' .
-			substr_replace( $script_path, '.asset.php', - strlen( '.js' ) )
-		)
-	);
-	if ( ! file_exists( $script_asset_path ) ) {
-		_doing_it_wrong(
-			__FUNCTION__,
-			sprintf(
-				/* translators: 1: Field name, 2: Block name. */
-				__( 'The asset file for the "%1$s" defined in "%2$s" block definition is missing.' ),
-				$field_name,
-				$metadata['name']
-			),
-			'5.5.0'
-		);
-		return false;
-	}
-	// Path needs to be normalized to work in Windows env.
-	$wpinc_path_norm  = wp_normalize_path( realpath( ABSPATH . WPINC ) );
-	$theme_path_norm  = wp_normalize_path( get_theme_file_path() );
-	$script_path_norm = wp_normalize_path( realpath( dirname( $metadata['file'] ) . '/' . $script_path ) );
-	$is_core_block    = isset( $metadata['file'] ) && 0 === strpos( $metadata['file'], $wpinc_path_norm );
-	$is_theme_block   = 0 === strpos( $script_path_norm, $theme_path_norm );
-
-	$script_uri = plugins_url( $script_path, $metadata['file'] );
-	if ( $is_core_block ) {
-		$script_uri = includes_url( str_replace( $wpinc_path_norm, '', $script_path_norm ) );
-	} elseif ( $is_theme_block ) {
-		$script_uri = get_theme_file_uri( str_replace( $theme_path_norm, '', $script_path_norm ) );
+	$script_path_norm    = wp_normalize_path( realpath( $path . '/' . $script_path ) );
+	$script_uri          = get_block_asset_url( $script_path_norm );
+	$script_dependencies = isset( $script_asset['dependencies'] ) ? $script_asset['dependencies'] : array();
+	$block_version       = isset( $metadata['version'] ) ? $metadata['version'] : false;
+	$script_version      = isset( $script_asset['version'] ) ? $script_asset['version'] : $block_version;
+	$script_args         = array();
+	if ( 'viewScript' === $field_name && $script_uri ) {
+		$script_args['strategy'] = 'defer';
 	}
 
-	$script_asset        = require $script_asset_path;
-	$script_dependencies = isset( $script_asset['dependencies'] ) ? $script_asset['dependencies'] : array();
-	$result              = wp_register_script(
+	$result = wp_register_script(
 		$script_handle,
 		$script_uri,
 		$script_dependencies,
-		isset( $script_asset['version'] ) ? $script_asset['version'] : false
+		$script_version,
+		$script_args
 	);
 	if ( ! $result ) {
 		return false;
@@ -145,71 +269,93 @@
  * generated handle name. It returns unprocessed style handle otherwise.
  *
  * @since 5.5.0
+ * @since 6.1.0 Added `$index` parameter.
  *
  * @param array  $metadata   Block metadata.
  * @param string $field_name Field name to pick from metadata.
+ * @param int    $index      Optional. Index of the style to register when multiple items passed.
+ *                           Default 0.
  * @return string|false Style handle provided directly or created through
  *                      style's registration, or false on failure.
  */
-function register_block_style_handle( $metadata, $field_name ) {
+function register_block_style_handle( $metadata, $field_name, $index = 0 ) {
 	if ( empty( $metadata[ $field_name ] ) ) {
 		return false;
 	}
-	$wpinc_path_norm = wp_normalize_path( realpath( ABSPATH . WPINC ) );
-	$theme_path_norm = wp_normalize_path( get_theme_file_path() );
-	$is_core_block   = isset( $metadata['file'] ) && 0 === strpos( $metadata['file'], $wpinc_path_norm );
+
+	$style_handle = $metadata[ $field_name ];
+	if ( is_array( $style_handle ) ) {
+		if ( empty( $style_handle[ $index ] ) ) {
+			return false;
+		}
+		$style_handle = $style_handle[ $index ];
+	}
+
+	$style_handle_name = generate_block_asset_handle( $metadata['name'], $field_name, $index );
+	// If the style handle is already registered, skip re-registering.
+	if ( wp_style_is( $style_handle_name, 'registered' ) ) {
+		return $style_handle_name;
+	}
+
+	static $wpinc_path_norm = '';
+	if ( ! $wpinc_path_norm ) {
+		$wpinc_path_norm = wp_normalize_path( realpath( ABSPATH . WPINC ) );
+	}
+
+	$is_core_block = isset( $metadata['file'] ) && str_starts_with( $metadata['file'], $wpinc_path_norm );
+	// Skip registering individual styles for each core block when a bundled version provided.
 	if ( $is_core_block && ! wp_should_load_separate_core_block_assets() ) {
 		return false;
 	}
 
+	$style_path      = remove_block_asset_path_prefix( $style_handle );
+	$is_style_handle = $style_handle === $style_path;
+	// Allow only passing style handles for core blocks.
+	if ( $is_core_block && ! $is_style_handle ) {
+		return false;
+	}
+	// Return the style handle unless it's the first item for every core block that requires special treatment.
+	if ( $is_style_handle && ! ( $is_core_block && 0 === $index ) ) {
+		return $style_handle;
+	}
+
 	// Check whether styles should have a ".min" suffix or not.
 	$suffix = SCRIPT_DEBUG ? '' : '.min';
-
-	$style_handle = $metadata[ $field_name ];
-	$style_path   = remove_block_asset_path_prefix( $metadata[ $field_name ] );
-
-	if ( $style_handle === $style_path && ! $is_core_block ) {
-		return $style_handle;
-	}
-
-	$style_uri = plugins_url( $style_path, $metadata['file'] );
 	if ( $is_core_block ) {
-		$style_path = "style$suffix.css";
-		$style_uri  = includes_url( 'blocks/' . str_replace( 'core/', '', $metadata['name'] ) . "/style$suffix.css" );
+		$style_path = ( 'editorStyle' === $field_name ) ? "editor{$suffix}.css" : "style{$suffix}.css";
 	}
 
 	$style_path_norm = wp_normalize_path( realpath( dirname( $metadata['file'] ) . '/' . $style_path ) );
-	$is_theme_block  = 0 === strpos( $style_path_norm, $theme_path_norm );
-
-	if ( $is_theme_block ) {
-		$style_uri = get_theme_file_uri( str_replace( $theme_path_norm, '', $style_path_norm ) );
-	}
+	$style_uri       = get_block_asset_url( $style_path_norm );
 
-	$style_handle   = generate_block_asset_handle( $metadata['name'], $field_name );
-	$block_dir      = dirname( $metadata['file'] );
-	$style_file     = realpath( "$block_dir/$style_path" );
-	$has_style_file = false !== $style_file;
-	$version        = ! $is_core_block && isset( $metadata['version'] ) ? $metadata['version'] : false;
-	$style_uri      = $has_style_file ? $style_uri : false;
-	$result         = wp_register_style(
-		$style_handle,
+	$version = ! $is_core_block && isset( $metadata['version'] ) ? $metadata['version'] : false;
+	$result  = wp_register_style(
+		$style_handle_name,
 		$style_uri,
 		array(),
 		$version
 	);
-	if ( file_exists( str_replace( '.css', '-rtl.css', $style_file ) ) ) {
-		wp_style_add_data( $style_handle, 'rtl', 'replace' );
-	}
-	if ( $has_style_file ) {
-		wp_style_add_data( $style_handle, 'path', $style_file );
+	if ( ! $result ) {
+		return false;
 	}
 
-	$rtl_file = str_replace( "$suffix.css", "-rtl$suffix.css", $style_file );
-	if ( is_rtl() && file_exists( $rtl_file ) ) {
-		wp_style_add_data( $style_handle, 'path', $rtl_file );
+	if ( $style_uri ) {
+		wp_style_add_data( $style_handle_name, 'path', $style_path_norm );
+
+		if ( $is_core_block ) {
+			$rtl_file = str_replace( "{$suffix}.css", "-rtl{$suffix}.css", $style_path_norm );
+		} else {
+			$rtl_file = str_replace( '.css', '-rtl.css', $style_path_norm );
+		}
+
+		if ( is_rtl() && file_exists( $rtl_file ) ) {
+			wp_style_add_data( $style_handle_name, 'rtl', 'replace' );
+			wp_style_add_data( $style_handle_name, 'suffix', $suffix );
+			wp_style_add_data( $style_handle_name, 'path', $rtl_file );
+		}
 	}
 
-	return $result ? $style_handle : false;
+	return $style_handle_name;
 }
 
 /**
@@ -235,6 +381,10 @@
  * @since 5.5.0
  * @since 5.7.0 Added support for `textdomain` field and i18n handling for all translatable fields.
  * @since 5.9.0 Added support for `variations` and `viewScript` fields.
+ * @since 6.1.0 Added support for `render` field.
+ * @since 6.3.0 Added `selectors` field.
+ * @since 6.4.0 Added support for `blockHooks` field.
+ * @since 6.5.0 Added support for `allowedBlocks`, `viewScriptModule`, and `viewStyle` fields.
  *
  * @param string $file_or_folder Path to the JSON file with metadata definition for
  *                               the block or path to the folder where the `block.json` file is located.
@@ -245,19 +395,47 @@
  * @return WP_Block_Type|false The registered block type on success, or false on failure.
  */
 function register_block_type_from_metadata( $file_or_folder, $args = array() ) {
-	$filename      = 'block.json';
-	$metadata_file = ( substr( $file_or_folder, -strlen( $filename ) ) !== $filename ) ?
-		trailingslashit( $file_or_folder ) . $filename :
+	/*
+	 * Get an array of metadata from a PHP file.
+	 * This improves performance for core blocks as it's only necessary to read a single PHP file
+	 * instead of reading a JSON file per-block, and then decoding from JSON to PHP.
+	 * Using a static variable ensures that the metadata is only read once per request.
+	 */
+	static $core_blocks_meta;
+	if ( ! $core_blocks_meta ) {
+		$core_blocks_meta = require ABSPATH . WPINC . '/blocks/blocks-json.php';
+	}
+
+	$metadata_file = ( ! str_ends_with( $file_or_folder, 'block.json' ) ) ?
+		trailingslashit( $file_or_folder ) . 'block.json' :
 		$file_or_folder;
-	if ( ! file_exists( $metadata_file ) ) {
+
+	$is_core_block = str_starts_with( $file_or_folder, ABSPATH . WPINC );
+	// If the block is not a core block, the metadata file must exist.
+	$metadata_file_exists = $is_core_block || file_exists( $metadata_file );
+	if ( ! $metadata_file_exists && empty( $args['name'] ) ) {
 		return false;
 	}
 
-	$metadata = wp_json_file_decode( $metadata_file, array( 'associative' => true ) );
-	if ( ! is_array( $metadata ) || empty( $metadata['name'] ) ) {
+	// Try to get metadata from the static cache for core blocks.
+	$metadata = array();
+	if ( $is_core_block ) {
+		$core_block_name = str_replace( ABSPATH . WPINC . '/blocks/', '', $file_or_folder );
+		if ( ! empty( $core_blocks_meta[ $core_block_name ] ) ) {
+			$metadata = $core_blocks_meta[ $core_block_name ];
+		}
+	}
+
+	// If metadata is not found in the static cache, read it from the file.
+	if ( $metadata_file_exists && empty( $metadata ) ) {
+		$metadata = wp_json_file_decode( $metadata_file, array( 'associative' => true ) );
+	}
+
+	if ( ! is_array( $metadata ) || ( empty( $metadata['name'] ) && empty( $args['name'] ) ) ) {
 		return false;
 	}
-	$metadata['file'] = wp_normalize_path( realpath( $metadata_file ) );
+
+	$metadata['file'] = $metadata_file_exists ? wp_normalize_path( realpath( $metadata_file ) ) : null;
 
 	/**
 	 * Filters the metadata provided for registering a block type.
@@ -269,12 +447,16 @@
 	$metadata = apply_filters( 'block_type_metadata', $metadata );
 
 	// Add `style` and `editor_style` for core blocks if missing.
-	if ( ! empty( $metadata['name'] ) && 0 === strpos( $metadata['name'], 'core/' ) ) {
+	if ( ! empty( $metadata['name'] ) && str_starts_with( $metadata['name'], 'core/' ) ) {
 		$block_name = str_replace( 'core/', '', $metadata['name'] );
 
 		if ( ! isset( $metadata['style'] ) ) {
 			$metadata['style'] = "wp-block-$block_name";
 		}
+		if ( current_theme_supports( 'wp-block-styles' ) && wp_should_load_separate_core_block_assets() ) {
+			$metadata['style']   = (array) $metadata['style'];
+			$metadata['style'][] = "wp-block-{$block_name}-theme";
+		}
 		if ( ! isset( $metadata['editorStyle'] ) ) {
 			$metadata['editorStyle'] = "wp-block-{$block_name}-editor";
 		}
@@ -283,6 +465,7 @@
 	$settings          = array();
 	$property_mappings = array(
 		'apiVersion'      => 'api_version',
+		'name'            => 'name',
 		'title'           => 'title',
 		'category'        => 'category',
 		'parent'          => 'parent',
@@ -293,10 +476,12 @@
 		'attributes'      => 'attributes',
 		'providesContext' => 'provides_context',
 		'usesContext'     => 'uses_context',
+		'selectors'       => 'selectors',
 		'supports'        => 'supports',
 		'styles'          => 'styles',
 		'variations'      => 'variations',
 		'example'         => 'example',
+		'allowedBlocks'   => 'allowed_blocks',
 	);
 	$textdomain        = ! empty( $metadata['textdomain'] ) ? $metadata['textdomain'] : null;
 	$i18n_schema       = get_block_metadata_i18n_schema();
@@ -304,45 +489,178 @@
 	foreach ( $property_mappings as $key => $mapped_key ) {
 		if ( isset( $metadata[ $key ] ) ) {
 			$settings[ $mapped_key ] = $metadata[ $key ];
-			if ( $textdomain && isset( $i18n_schema->$key ) ) {
+			if ( $metadata_file_exists && $textdomain && isset( $i18n_schema->$key ) ) {
 				$settings[ $mapped_key ] = translate_settings_using_i18n_schema( $i18n_schema->$key, $settings[ $key ], $textdomain );
 			}
 		}
 	}
 
-	if ( ! empty( $metadata['editorScript'] ) ) {
-		$settings['editor_script'] = register_block_script_handle(
-			$metadata,
-			'editorScript'
+	if ( ! empty( $metadata['render'] ) ) {
+		$template_path = wp_normalize_path(
+			realpath(
+				dirname( $metadata['file'] ) . '/' .
+				remove_block_asset_path_prefix( $metadata['render'] )
+			)
 		);
+		if ( $template_path ) {
+			/**
+			 * Renders the block on the server.
+			 *
+			 * @since 6.1.0
+			 *
+			 * @param array    $attributes Block attributes.
+			 * @param string   $content    Block default content.
+			 * @param WP_Block $block      Block instance.
+			 *
+			 * @return string Returns the block content.
+			 */
+			$settings['render_callback'] = static function ( $attributes, $content, $block ) use ( $template_path ) {
+				ob_start();
+				require $template_path;
+				return ob_get_clean();
+			};
+		}
 	}
 
-	if ( ! empty( $metadata['script'] ) ) {
-		$settings['script'] = register_block_script_handle(
-			$metadata,
-			'script'
-		);
+	$settings = array_merge( $settings, $args );
+
+	$script_fields = array(
+		'editorScript' => 'editor_script_handles',
+		'script'       => 'script_handles',
+		'viewScript'   => 'view_script_handles',
+	);
+	foreach ( $script_fields as $metadata_field_name => $settings_field_name ) {
+		if ( ! empty( $settings[ $metadata_field_name ] ) ) {
+			$metadata[ $metadata_field_name ] = $settings[ $metadata_field_name ];
+		}
+		if ( ! empty( $metadata[ $metadata_field_name ] ) ) {
+			$scripts           = $metadata[ $metadata_field_name ];
+			$processed_scripts = array();
+			if ( is_array( $scripts ) ) {
+				for ( $index = 0; $index < count( $scripts ); $index++ ) {
+					$result = register_block_script_handle(
+						$metadata,
+						$metadata_field_name,
+						$index
+					);
+					if ( $result ) {
+						$processed_scripts[] = $result;
+					}
+				}
+			} else {
+				$result = register_block_script_handle(
+					$metadata,
+					$metadata_field_name
+				);
+				if ( $result ) {
+					$processed_scripts[] = $result;
+				}
+			}
+			$settings[ $settings_field_name ] = $processed_scripts;
+		}
 	}
 
-	if ( ! empty( $metadata['viewScript'] ) ) {
-		$settings['view_script'] = register_block_script_handle(
-			$metadata,
-			'viewScript'
-		);
+	$module_fields = array(
+		'viewScriptModule' => 'view_script_module_ids',
+	);
+	foreach ( $module_fields as $metadata_field_name => $settings_field_name ) {
+		if ( ! empty( $settings[ $metadata_field_name ] ) ) {
+			$metadata[ $metadata_field_name ] = $settings[ $metadata_field_name ];
+		}
+		if ( ! empty( $metadata[ $metadata_field_name ] ) ) {
+			$modules           = $metadata[ $metadata_field_name ];
+			$processed_modules = array();
+			if ( is_array( $modules ) ) {
+				for ( $index = 0; $index < count( $modules ); $index++ ) {
+					$result = register_block_script_module_id(
+						$metadata,
+						$metadata_field_name,
+						$index
+					);
+					if ( $result ) {
+						$processed_modules[] = $result;
+					}
+				}
+			} else {
+				$result = register_block_script_module_id(
+					$metadata,
+					$metadata_field_name
+				);
+				if ( $result ) {
+					$processed_modules[] = $result;
+				}
+			}
+			$settings[ $settings_field_name ] = $processed_modules;
+		}
 	}
 
-	if ( ! empty( $metadata['editorStyle'] ) ) {
-		$settings['editor_style'] = register_block_style_handle(
-			$metadata,
-			'editorStyle'
-		);
+	$style_fields = array(
+		'editorStyle' => 'editor_style_handles',
+		'style'       => 'style_handles',
+		'viewStyle'   => 'view_style_handles',
+	);
+	foreach ( $style_fields as $metadata_field_name => $settings_field_name ) {
+		if ( ! empty( $settings[ $metadata_field_name ] ) ) {
+			$metadata[ $metadata_field_name ] = $settings[ $metadata_field_name ];
+		}
+		if ( ! empty( $metadata[ $metadata_field_name ] ) ) {
+			$styles           = $metadata[ $metadata_field_name ];
+			$processed_styles = array();
+			if ( is_array( $styles ) ) {
+				for ( $index = 0; $index < count( $styles ); $index++ ) {
+					$result = register_block_style_handle(
+						$metadata,
+						$metadata_field_name,
+						$index
+					);
+					if ( $result ) {
+						$processed_styles[] = $result;
+					}
+				}
+			} else {
+				$result = register_block_style_handle(
+					$metadata,
+					$metadata_field_name
+				);
+				if ( $result ) {
+					$processed_styles[] = $result;
+				}
+			}
+			$settings[ $settings_field_name ] = $processed_styles;
+		}
 	}
 
-	if ( ! empty( $metadata['style'] ) ) {
-		$settings['style'] = register_block_style_handle(
-			$metadata,
-			'style'
+	if ( ! empty( $metadata['blockHooks'] ) ) {
+		/**
+		 * Map camelCased position string (from block.json) to snake_cased block type position.
+		 *
+		 * @var array
+		 */
+		$position_mappings = array(
+			'before'     => 'before',
+			'after'      => 'after',
+			'firstChild' => 'first_child',
+			'lastChild'  => 'last_child',
 		);
+
+		$settings['block_hooks'] = array();
+		foreach ( $metadata['blockHooks'] as $anchor_block_name => $position ) {
+			// Avoid infinite recursion (hooking to itself).
+			if ( $metadata['name'] === $anchor_block_name ) {
+				_doing_it_wrong(
+					__METHOD__,
+					__( 'Cannot hook block to itself.' ),
+					'6.4.0'
+				);
+				continue;
+			}
+
+			if ( ! isset( $position_mappings[ $position ] ) ) {
+				continue;
+			}
+
+			$settings['block_hooks'][ $anchor_block_name ] = $position_mappings[ $position ];
+		}
 	}
 
 	/**
@@ -353,14 +671,9 @@
 	 * @param array $settings Array of determined settings for registering a block type.
 	 * @param array $metadata Metadata provided for registering a block type.
 	 */
-	$settings = apply_filters(
-		'block_type_metadata_settings',
-		array_merge(
-			$settings,
-			$args
-		),
-		$metadata
-	);
+	$settings = apply_filters( 'block_type_metadata_settings', $settings, $metadata );
+
+	$metadata['name'] = ! empty( $settings['name'] ) ? $settings['name'] : $metadata['name'];
 
 	return WP_Block_Type_Registry::get_instance()->register(
 		$metadata['name'],
@@ -425,12 +738,15 @@
 function has_blocks( $post = null ) {
 	if ( ! is_string( $post ) ) {
 		$wp_post = get_post( $post );
-		if ( $wp_post instanceof WP_Post ) {
-			$post = $wp_post->post_content;
+
+		if ( ! $wp_post instanceof WP_Post ) {
+			return false;
 		}
+
+		$post = $wp_post->post_content;
 	}
 
-	return false !== strpos( (string) $post, '<!-- wp:' );
+	return str_contains( (string) $post, '<!-- wp:' );
 }
 
 /**
@@ -438,7 +754,8 @@
  *
  * This test optimizes for performance rather than strict accuracy, detecting
  * whether the block type exists but not validating its structure and not checking
- * reusable blocks. For strict accuracy, you should use the block parser on post content.
+ * synced patterns (formerly called reusable blocks). For strict accuracy,
+ * you should use the block parser on post content.
  *
  * @since 5.0.0
  *
@@ -466,12 +783,12 @@
 	 * This matches behavior for WordPress 5.0.0 - 5.3.0 in matching blocks by
 	 * their serialized names.
 	 */
-	if ( false === strpos( $block_name, '/' ) ) {
+	if ( ! str_contains( $block_name, '/' ) ) {
 		$block_name = 'core/' . $block_name;
 	}
 
 	// Test for existence of block by its fully qualified name.
-	$has_block = false !== strpos( $post, '<!-- wp:' . $block_name . ' ' );
+	$has_block = str_contains( $post, '<!-- wp:' . $block_name . ' ' );
 
 	if ( ! $has_block ) {
 		/*
@@ -480,7 +797,7 @@
 		 */
 		$serialized_block_name = strip_core_block_namespace( $block_name );
 		if ( $serialized_block_name !== $block_name ) {
-			$has_block = false !== strpos( $post, '<!-- wp:' . $serialized_block_name . ' ' );
+			$has_block = str_contains( $post, '<!-- wp:' . $serialized_block_name . ' ' );
 		}
 	}
 
@@ -508,6 +825,470 @@
 }
 
 /**
+ * Retrieves block types hooked into the given block, grouped by anchor block type and the relative position.
+ *
+ * @since 6.4.0
+ *
+ * @return array[] Array of block types grouped by anchor block type and the relative position.
+ */
+function get_hooked_blocks() {
+	$block_types   = WP_Block_Type_Registry::get_instance()->get_all_registered();
+	$hooked_blocks = array();
+	foreach ( $block_types as $block_type ) {
+		if ( ! ( $block_type instanceof WP_Block_Type ) || ! is_array( $block_type->block_hooks ) ) {
+			continue;
+		}
+		foreach ( $block_type->block_hooks as $anchor_block_type => $relative_position ) {
+			if ( ! isset( $hooked_blocks[ $anchor_block_type ] ) ) {
+				$hooked_blocks[ $anchor_block_type ] = array();
+			}
+			if ( ! isset( $hooked_blocks[ $anchor_block_type ][ $relative_position ] ) ) {
+				$hooked_blocks[ $anchor_block_type ][ $relative_position ] = array();
+			}
+			$hooked_blocks[ $anchor_block_type ][ $relative_position ][] = $block_type->name;
+		}
+	}
+
+	return $hooked_blocks;
+}
+
+/**
+ * Returns the markup for blocks hooked to the given anchor block in a specific relative position.
+ *
+ * @since 6.5.0
+ * @access private
+ *
+ * @param array                           $parsed_anchor_block The anchor block, in parsed block array format.
+ * @param string                          $relative_position   The relative position of the hooked blocks.
+ *                                                             Can be one of 'before', 'after', 'first_child', or 'last_child'.
+ * @param array                           $hooked_blocks       An array of hooked block types, grouped by anchor block and relative position.
+ * @param WP_Block_Template|WP_Post|array $context             The block template, template part, or pattern that the anchor block belongs to.
+ * @return string
+ */
+function insert_hooked_blocks( &$parsed_anchor_block, $relative_position, $hooked_blocks, $context ) {
+	$anchor_block_type  = $parsed_anchor_block['blockName'];
+	$hooked_block_types = isset( $hooked_blocks[ $anchor_block_type ][ $relative_position ] )
+		? $hooked_blocks[ $anchor_block_type ][ $relative_position ]
+		: array();
+
+	/**
+	 * Filters the list of hooked block types for a given anchor block type and relative position.
+	 *
+	 * @since 6.4.0
+	 *
+	 * @param string[]                        $hooked_block_types The list of hooked block types.
+	 * @param string                          $relative_position  The relative position of the hooked blocks.
+	 *                                                            Can be one of 'before', 'after', 'first_child', or 'last_child'.
+	 * @param string                          $anchor_block_type  The anchor block type.
+	 * @param WP_Block_Template|WP_Post|array $context            The block template, template part, `wp_navigation` post type,
+	 *                                                            or pattern that the anchor block belongs to.
+	 */
+	$hooked_block_types = apply_filters( 'hooked_block_types', $hooked_block_types, $relative_position, $anchor_block_type, $context );
+
+	$markup = '';
+	foreach ( $hooked_block_types as $hooked_block_type ) {
+		$parsed_hooked_block = array(
+			'blockName'    => $hooked_block_type,
+			'attrs'        => array(),
+			'innerBlocks'  => array(),
+			'innerContent' => array(),
+		);
+
+		/**
+		 * Filters the parsed block array for a given hooked block.
+		 *
+		 * @since 6.5.0
+		 *
+		 * @param array|null                      $parsed_hooked_block The parsed block array for the given hooked block type, or null to suppress the block.
+		 * @param string                          $hooked_block_type   The hooked block type name.
+		 * @param string                          $relative_position   The relative position of the hooked block.
+		 * @param array                           $parsed_anchor_block The anchor block, in parsed block array format.
+		 * @param WP_Block_Template|WP_Post|array $context             The block template, template part, `wp_navigation` post type,
+		 *                                                             or pattern that the anchor block belongs to.
+		 */
+		$parsed_hooked_block = apply_filters( 'hooked_block', $parsed_hooked_block, $hooked_block_type, $relative_position, $parsed_anchor_block, $context );
+
+		/**
+		 * Filters the parsed block array for a given hooked block.
+		 *
+		 * The dynamic portion of the hook name, `$hooked_block_type`, refers to the block type name of the specific hooked block.
+		 *
+		 * @since 6.5.0
+		 *
+		 * @param array|null                      $parsed_hooked_block The parsed block array for the given hooked block type, or null to suppress the block.
+		 * @param string                          $hooked_block_type   The hooked block type name.
+		 * @param string                          $relative_position   The relative position of the hooked block.
+		 * @param array                           $parsed_anchor_block The anchor block, in parsed block array format.
+		 * @param WP_Block_Template|WP_Post|array $context             The block template, template part, `wp_navigation` post type,
+		 *                                                             or pattern that the anchor block belongs to.
+		 */
+		$parsed_hooked_block = apply_filters( "hooked_block_{$hooked_block_type}", $parsed_hooked_block, $hooked_block_type, $relative_position, $parsed_anchor_block, $context );
+
+		if ( null === $parsed_hooked_block ) {
+			continue;
+		}
+
+		// It's possible that the filter returned a block of a different type, so we explicitly
+		// look for the original `$hooked_block_type` in the `ignoredHookedBlocks` metadata.
+		if (
+			! isset( $parsed_anchor_block['attrs']['metadata']['ignoredHookedBlocks'] ) ||
+			! in_array( $hooked_block_type, $parsed_anchor_block['attrs']['metadata']['ignoredHookedBlocks'], true )
+		) {
+			$markup .= serialize_block( $parsed_hooked_block );
+		}
+	}
+
+	return $markup;
+}
+
+/**
+ * Adds a list of hooked block types to an anchor block's ignored hooked block types.
+ *
+ * This function is meant for internal use only.
+ *
+ * @since 6.5.0
+ * @access private
+ *
+ * @param array                           $parsed_anchor_block The anchor block, in parsed block array format.
+ * @param string                          $relative_position   The relative position of the hooked blocks.
+ *                                                             Can be one of 'before', 'after', 'first_child', or 'last_child'.
+ * @param array                           $hooked_blocks       An array of hooked block types, grouped by anchor block and relative position.
+ * @param WP_Block_Template|WP_Post|array $context             The block template, template part, or pattern that the anchor block belongs to.
+ * @return string Empty string.
+ */
+function set_ignored_hooked_blocks_metadata( &$parsed_anchor_block, $relative_position, $hooked_blocks, $context ) {
+	$anchor_block_type  = $parsed_anchor_block['blockName'];
+	$hooked_block_types = isset( $hooked_blocks[ $anchor_block_type ][ $relative_position ] )
+		? $hooked_blocks[ $anchor_block_type ][ $relative_position ]
+		: array();
+
+	/** This filter is documented in wp-includes/blocks.php */
+	$hooked_block_types = apply_filters( 'hooked_block_types', $hooked_block_types, $relative_position, $anchor_block_type, $context );
+	if ( empty( $hooked_block_types ) ) {
+		return '';
+	}
+
+	foreach ( $hooked_block_types as $index => $hooked_block_type ) {
+		$parsed_hooked_block = array(
+			'blockName'    => $hooked_block_type,
+			'attrs'        => array(),
+			'innerBlocks'  => array(),
+			'innerContent' => array(),
+		);
+
+		/** This filter is documented in wp-includes/blocks.php */
+		$parsed_hooked_block = apply_filters( 'hooked_block', $parsed_hooked_block, $hooked_block_type, $relative_position, $parsed_anchor_block, $context );
+
+		/** This filter is documented in wp-includes/blocks.php */
+		$parsed_hooked_block = apply_filters( "hooked_block_{$hooked_block_type}", $parsed_hooked_block, $hooked_block_type, $relative_position, $parsed_anchor_block, $context );
+
+		if ( null === $parsed_hooked_block ) {
+			unset( $hooked_block_types[ $index ] );
+		}
+	}
+
+	$previously_ignored_hooked_blocks = isset( $parsed_anchor_block['attrs']['metadata']['ignoredHookedBlocks'] )
+		? $parsed_anchor_block['attrs']['metadata']['ignoredHookedBlocks']
+		: array();
+
+	$parsed_anchor_block['attrs']['metadata']['ignoredHookedBlocks'] = array_unique(
+		array_merge(
+			$previously_ignored_hooked_blocks,
+			$hooked_block_types
+		)
+	);
+
+	// Markup for the hooked blocks has already been created (in `insert_hooked_blocks`).
+	return '';
+}
+
+/**
+ * Runs the hooked blocks algorithm on the given content.
+ *
+ * @since 6.6.0
+ * @access private
+ *
+ * @param string                          $content  Serialized content.
+ * @param WP_Block_Template|WP_Post|array $context  A block template, template part, `wp_navigation` post object,
+ *                                                  or pattern that the blocks belong to.
+ * @param callable                        $callback A function that will be called for each block to generate
+ *                                                  the markup for a given list of blocks that are hooked to it.
+ *                                                  Default: 'insert_hooked_blocks'.
+ * @return string The serialized markup.
+ */
+function apply_block_hooks_to_content( $content, $context, $callback = 'insert_hooked_blocks' ) {
+	$hooked_blocks = get_hooked_blocks();
+	if ( empty( $hooked_blocks ) && ! has_filter( 'hooked_block_types' ) ) {
+		return $content;
+	}
+
+	$blocks = parse_blocks( $content );
+
+	$before_block_visitor = make_before_block_visitor( $hooked_blocks, $context, $callback );
+	$after_block_visitor  = make_after_block_visitor( $hooked_blocks, $context, $callback );
+
+	return traverse_and_serialize_blocks( $blocks, $before_block_visitor, $after_block_visitor );
+}
+
+/**
+ * Accepts the serialized markup of a block and its inner blocks, and returns serialized markup of the inner blocks.
+ *
+ * @since 6.6.0
+ * @access private
+ *
+ * @param string $serialized_block The serialized markup of a block and its inner blocks.
+ * @return string The serialized markup of the inner blocks.
+ */
+function remove_serialized_parent_block( $serialized_block ) {
+	$start = strpos( $serialized_block, '-->' ) + strlen( '-->' );
+	$end   = strrpos( $serialized_block, '<!--' );
+	return substr( $serialized_block, $start, $end - $start );
+}
+
+/**
+ * Updates the wp_postmeta with the list of ignored hooked blocks where the inner blocks are stored as post content.
+ * Currently only supports `wp_navigation` post types.
+ *
+ * @since 6.6.0
+ * @access private
+ *
+ * @param stdClass $post Post object.
+ * @return stdClass The updated post object.
+ */
+function update_ignored_hooked_blocks_postmeta( $post ) {
+	/*
+	 * In this scenario the user has likely tried to create a navigation via the REST API.
+	 * In which case we won't have a post ID to work with and store meta against.
+	 */
+	if ( empty( $post->ID ) ) {
+		return $post;
+	}
+
+	/*
+	 * Skip meta generation when consumers intentionally update specific Navigation fields
+	 * and omit the content update.
+	 */
+	if ( ! isset( $post->post_content ) ) {
+		return $post;
+	}
+
+	/*
+	 * Skip meta generation when the post content is not a navigation block.
+	 */
+	if ( ! isset( $post->post_type ) || 'wp_navigation' !== $post->post_type ) {
+		return $post;
+	}
+
+	$attributes = array();
+
+	$ignored_hooked_blocks = get_post_meta( $post->ID, '_wp_ignored_hooked_blocks', true );
+	if ( ! empty( $ignored_hooked_blocks ) ) {
+		$ignored_hooked_blocks  = json_decode( $ignored_hooked_blocks, true );
+		$attributes['metadata'] = array(
+			'ignoredHookedBlocks' => $ignored_hooked_blocks,
+		);
+	}
+
+	$markup = get_comment_delimited_block_content(
+		'core/navigation',
+		$attributes,
+		$post->post_content
+	);
+
+	$serialized_block = apply_block_hooks_to_content( $markup, get_post( $post->ID ), 'set_ignored_hooked_blocks_metadata' );
+	$root_block       = parse_blocks( $serialized_block )[0];
+
+	$ignored_hooked_blocks = isset( $root_block['attrs']['metadata']['ignoredHookedBlocks'] )
+		? $root_block['attrs']['metadata']['ignoredHookedBlocks']
+		: array();
+
+	if ( ! empty( $ignored_hooked_blocks ) ) {
+		$existing_ignored_hooked_blocks = get_post_meta( $post->ID, '_wp_ignored_hooked_blocks', true );
+		if ( ! empty( $existing_ignored_hooked_blocks ) ) {
+			$existing_ignored_hooked_blocks = json_decode( $existing_ignored_hooked_blocks, true );
+			$ignored_hooked_blocks          = array_unique( array_merge( $ignored_hooked_blocks, $existing_ignored_hooked_blocks ) );
+		}
+		update_post_meta( $post->ID, '_wp_ignored_hooked_blocks', json_encode( $ignored_hooked_blocks ) );
+	}
+
+	$post->post_content = remove_serialized_parent_block( $serialized_block );
+	return $post;
+}
+
+/**
+ * Returns the markup for blocks hooked to the given anchor block in a specific relative position and then
+ * adds a list of hooked block types to an anchor block's ignored hooked block types.
+ *
+ * This function is meant for internal use only.
+ *
+ * @since 6.6.0
+ * @access private
+ *
+ * @param array                           $parsed_anchor_block The anchor block, in parsed block array format.
+ * @param string                          $relative_position   The relative position of the hooked blocks.
+ *                                                             Can be one of 'before', 'after', 'first_child', or 'last_child'.
+ * @param array                           $hooked_blocks       An array of hooked block types, grouped by anchor block and relative position.
+ * @param WP_Block_Template|WP_Post|array $context             The block template, template part, or pattern that the anchor block belongs to.
+ * @return string
+ */
+function insert_hooked_blocks_and_set_ignored_hooked_blocks_metadata( &$parsed_anchor_block, $relative_position, $hooked_blocks, $context ) {
+	$markup  = insert_hooked_blocks( $parsed_anchor_block, $relative_position, $hooked_blocks, $context );
+	$markup .= set_ignored_hooked_blocks_metadata( $parsed_anchor_block, $relative_position, $hooked_blocks, $context );
+
+	return $markup;
+}
+
+/**
+ * Hooks into the REST API response for the core/navigation block and adds the first and last inner blocks.
+ *
+ * @since 6.6.0
+ *
+ * @param WP_REST_Response $response The response object.
+ * @param WP_Post          $post     Post object.
+ * @return WP_REST_Response The response object.
+ */
+function insert_hooked_blocks_into_rest_response( $response, $post ) {
+	if ( ! isset( $response->data['content']['raw'] ) || ! isset( $response->data['content']['rendered'] ) ) {
+		return $response;
+	}
+
+	$attributes            = array();
+	$ignored_hooked_blocks = get_post_meta( $post->ID, '_wp_ignored_hooked_blocks', true );
+	if ( ! empty( $ignored_hooked_blocks ) ) {
+		$ignored_hooked_blocks  = json_decode( $ignored_hooked_blocks, true );
+		$attributes['metadata'] = array(
+			'ignoredHookedBlocks' => $ignored_hooked_blocks,
+		);
+	}
+	$content = get_comment_delimited_block_content(
+		'core/navigation',
+		$attributes,
+		$response->data['content']['raw']
+	);
+
+	$content = apply_block_hooks_to_content( $content, $post );
+
+	// Remove mock Navigation block wrapper.
+	$content = remove_serialized_parent_block( $content );
+
+	$response->data['content']['raw'] = $content;
+
+	/** This filter is documented in wp-includes/post-template.php */
+	$response->data['content']['rendered'] = apply_filters( 'the_content', $content );
+
+	return $response;
+}
+
+/**
+ * Returns a function that injects the theme attribute into, and hooked blocks before, a given block.
+ *
+ * The returned function can be used as `$pre_callback` argument to `traverse_and_serialize_block(s)`,
+ * where it will inject the `theme` attribute into all Template Part blocks, and prepend the markup for
+ * any blocks hooked `before` the given block and as its parent's `first_child`, respectively.
+ *
+ * This function is meant for internal use only.
+ *
+ * @since 6.4.0
+ * @since 6.5.0 Added $callback argument.
+ * @access private
+ *
+ * @param array                           $hooked_blocks An array of blocks hooked to another given block.
+ * @param WP_Block_Template|WP_Post|array $context       A block template, template part, `wp_navigation` post object,
+ *                                                       or pattern that the blocks belong to.
+ * @param callable                        $callback      A function that will be called for each block to generate
+ *                                                       the markup for a given list of blocks that are hooked to it.
+ *                                                       Default: 'insert_hooked_blocks'.
+ * @return callable A function that returns the serialized markup for the given block,
+ *                  including the markup for any hooked blocks before it.
+ */
+function make_before_block_visitor( $hooked_blocks, $context, $callback = 'insert_hooked_blocks' ) {
+	/**
+	 * Injects hooked blocks before the given block, injects the `theme` attribute into Template Part blocks, and returns the serialized markup.
+	 *
+	 * If the current block is a Template Part block, inject the `theme` attribute.
+	 * Furthermore, prepend the markup for any blocks hooked `before` the given block and as its parent's
+	 * `first_child`, respectively, to the serialized markup for the given block.
+	 *
+	 * @param array $block        The block to inject the theme attribute into, and hooked blocks before. Passed by reference.
+	 * @param array $parent_block The parent block of the given block. Passed by reference. Default null.
+	 * @param array $prev         The previous sibling block of the given block. Default null.
+	 * @return string The serialized markup for the given block, with the markup for any hooked blocks prepended to it.
+	 */
+	return function ( &$block, &$parent_block = null, $prev = null ) use ( $hooked_blocks, $context, $callback ) {
+		_inject_theme_attribute_in_template_part_block( $block );
+
+		$markup = '';
+
+		if ( $parent_block && ! $prev ) {
+			// Candidate for first-child insertion.
+			$markup .= call_user_func_array(
+				$callback,
+				array( &$parent_block, 'first_child', $hooked_blocks, $context )
+			);
+		}
+
+		$markup .= call_user_func_array(
+			$callback,
+			array( &$block, 'before', $hooked_blocks, $context )
+		);
+
+		return $markup;
+	};
+}
+
+/**
+ * Returns a function that injects the hooked blocks after a given block.
+ *
+ * The returned function can be used as `$post_callback` argument to `traverse_and_serialize_block(s)`,
+ * where it will append the markup for any blocks hooked `after` the given block and as its parent's
+ * `last_child`, respectively.
+ *
+ * This function is meant for internal use only.
+ *
+ * @since 6.4.0
+ * @since 6.5.0 Added $callback argument.
+ * @access private
+ *
+ * @param array                           $hooked_blocks An array of blocks hooked to another block.
+ * @param WP_Block_Template|WP_Post|array $context       A block template, template part, `wp_navigation` post object,
+ *                                                       or pattern that the blocks belong to.
+ * @param callable                        $callback      A function that will be called for each block to generate
+ *                                                       the markup for a given list of blocks that are hooked to it.
+ *                                                       Default: 'insert_hooked_blocks'.
+ * @return callable A function that returns the serialized markup for the given block,
+ *                  including the markup for any hooked blocks after it.
+ */
+function make_after_block_visitor( $hooked_blocks, $context, $callback = 'insert_hooked_blocks' ) {
+	/**
+	 * Injects hooked blocks after the given block, and returns the serialized markup.
+	 *
+	 * Append the markup for any blocks hooked `after` the given block and as its parent's
+	 * `last_child`, respectively, to the serialized markup for the given block.
+	 *
+	 * @param array $block        The block to inject the hooked blocks after. Passed by reference.
+	 * @param array $parent_block The parent block of the given block. Passed by reference. Default null.
+	 * @param array $next         The next sibling block of the given block. Default null.
+	 * @return string The serialized markup for the given block, with the markup for any hooked blocks appended to it.
+	 */
+	return function ( &$block, &$parent_block = null, $next = null ) use ( $hooked_blocks, $context, $callback ) {
+		$markup = call_user_func_array(
+			$callback,
+			array( &$block, 'after', $hooked_blocks, $context )
+		);
+
+		if ( $parent_block && ! $next ) {
+			// Candidate for last-child insertion.
+			$markup .= call_user_func_array(
+				$callback,
+				array( &$parent_block, 'last_child', $hooked_blocks, $context )
+			);
+		}
+
+		return $markup;
+	};
+}
+
+/**
  * Given an array of attributes, returns a string in the serialized attributes
  * format prepared for post content.
  *
@@ -542,11 +1323,12 @@
  *
  * @since 5.3.1
  *
- * @param string $block_name Original block name.
+ * @param string|null $block_name Optional. Original block name. Null if the block name is unknown,
+ *                                e.g. Classic blocks have their name set to null. Default null.
  * @return string Block name to use for serialization.
  */
 function strip_core_block_namespace( $block_name = null ) {
-	if ( is_string( $block_name ) && 0 === strpos( $block_name, 'core/' ) ) {
+	if ( is_string( $block_name ) && str_starts_with( $block_name, 'core/' ) ) {
 		return substr( $block_name, 5 );
 	}
 
@@ -596,7 +1378,17 @@
  *
  * @since 5.3.1
  *
- * @param array $block A representative array of a single parsed block object. See WP_Block_Parser_Block.
+ * @param array $block {
+ *     A representative array of a single parsed block object. See WP_Block_Parser_Block.
+ *
+ *     @type string   $blockName    Name of block.
+ *     @type array    $attrs        Attributes from block comment delimiters.
+ *     @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+ *                                  have the same structure as this one.
+ *     @type string   $innerHTML    HTML from inside block comment delimiters.
+ *     @type array    $innerContent List of string fragments and null markers where
+ *                                  inner blocks were found.
+ * }
  * @return string String of rendered HTML.
  */
 function serialize_block( $block ) {
@@ -619,12 +1411,26 @@
 }
 
 /**
- * Returns a joined string of the aggregate serialization of the given parsed
- * blocks.
+ * Returns a joined string of the aggregate serialization of the given
+ * parsed blocks.
  *
  * @since 5.3.1
  *
- * @param array[] $blocks An array of representative arrays of parsed block objects. See serialize_block().
+ * @param array[] $blocks {
+ *     Array of block structures.
+ *
+ *     @type array ...$0 {
+ *         A representative array of a single parsed block object. See WP_Block_Parser_Block.
+ *
+ *         @type string   $blockName    Name of block.
+ *         @type array    $attrs        Attributes from block comment delimiters.
+ *         @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+ *                                      have the same structure as this one.
+ *         @type string   $innerHTML    HTML from inside block comment delimiters.
+ *         @type array    $innerContent List of string fragments and null markers where
+ *                                      inner blocks were found.
+ *     }
+ * }
  * @return string String of rendered HTML.
  */
 function serialize_blocks( $blocks ) {
@@ -632,21 +1438,256 @@
 }
 
 /**
- * Filters and sanitizes block content to remove non-allowable HTML from
- * parsed block attribute values.
+ * Traverses a parsed block tree and applies callbacks before and after serializing it.
+ *
+ * Recursively traverses the block and its inner blocks and applies the two callbacks provided as
+ * arguments, the first one before serializing the block, and the second one after serializing it.
+ * If either callback returns a string value, it will be prepended and appended to the serialized
+ * block markup, respectively.
+ *
+ * The callbacks will receive a reference to the current block as their first argument, so that they
+ * can also modify it, and the current block's parent block as second argument. Finally, the
+ * `$pre_callback` receives the previous block, whereas the `$post_callback` receives
+ * the next block as third argument.
+ *
+ * Serialized blocks are returned including comment delimiters, and with all attributes serialized.
+ *
+ * This function should be used when there is a need to modify the saved block, or to inject markup
+ * into the return value. Prefer `serialize_block` when preparing a block to be saved to post content.
+ *
+ * This function is meant for internal use only.
+ *
+ * @since 6.4.0
+ * @access private
+ *
+ * @see serialize_block()
+ *
+ * @param array    $block         A representative array of a single parsed block object. See WP_Block_Parser_Block.
+ * @param callable $pre_callback  Callback to run on each block in the tree before it is traversed and serialized.
+ *                                It is called with the following arguments: &$block, $parent_block, $previous_block.
+ *                                Its string return value will be prepended to the serialized block markup.
+ * @param callable $post_callback Callback to run on each block in the tree after it is traversed and serialized.
+ *                                It is called with the following arguments: &$block, $parent_block, $next_block.
+ *                                Its string return value will be appended to the serialized block markup.
+ * @return string Serialized block markup.
+ */
+function traverse_and_serialize_block( $block, $pre_callback = null, $post_callback = null ) {
+	$block_content = '';
+	$block_index   = 0;
+
+	foreach ( $block['innerContent'] as $chunk ) {
+		if ( is_string( $chunk ) ) {
+			$block_content .= $chunk;
+		} else {
+			$inner_block = $block['innerBlocks'][ $block_index ];
+
+			if ( is_callable( $pre_callback ) ) {
+				$prev = 0 === $block_index
+					? null
+					: $block['innerBlocks'][ $block_index - 1 ];
+
+				$block_content .= call_user_func_array(
+					$pre_callback,
+					array( &$inner_block, &$block, $prev )
+				);
+			}
+
+			if ( is_callable( $post_callback ) ) {
+				$next = count( $block['innerBlocks'] ) - 1 === $block_index
+					? null
+					: $block['innerBlocks'][ $block_index + 1 ];
+
+				$post_markup = call_user_func_array(
+					$post_callback,
+					array( &$inner_block, &$block, $next )
+				);
+			}
+
+			$block_content .= traverse_and_serialize_block( $inner_block, $pre_callback, $post_callback );
+			$block_content .= isset( $post_markup ) ? $post_markup : '';
+
+			++$block_index;
+		}
+	}
+
+	if ( ! is_array( $block['attrs'] ) ) {
+		$block['attrs'] = array();
+	}
+
+	return get_comment_delimited_block_content(
+		$block['blockName'],
+		$block['attrs'],
+		$block_content
+	);
+}
+
+/**
+ * Replaces patterns in a block tree with their content.
+ *
+ * @since 6.6.0
+ *
+ * @param array $blocks An array blocks.
+ *
+ * @return array An array of blocks with patterns replaced by their content.
+ */
+function resolve_pattern_blocks( $blocks ) {
+	static $inner_content;
+	// Keep track of seen references to avoid infinite loops.
+	static $seen_refs = array();
+	$i                = 0;
+	while ( $i < count( $blocks ) ) {
+		if ( 'core/pattern' === $blocks[ $i ]['blockName'] ) {
+			$attrs = $blocks[ $i ]['attrs'];
+
+			if ( empty( $attrs['slug'] ) ) {
+				++$i;
+				continue;
+			}
+
+			$slug = $attrs['slug'];
+
+			if ( isset( $seen_refs[ $slug ] ) ) {
+				// Skip recursive patterns.
+				array_splice( $blocks, $i, 1 );
+				continue;
+			}
+
+			$registry = WP_Block_Patterns_Registry::get_instance();
+			$pattern  = $registry->get_registered( $slug );
+
+			// Skip unknown patterns.
+			if ( ! $pattern ) {
+				++$i;
+				continue;
+			}
+
+			$blocks_to_insert   = parse_blocks( $pattern['content'] );
+			$seen_refs[ $slug ] = true;
+			$prev_inner_content = $inner_content;
+			$inner_content      = null;
+			$blocks_to_insert   = resolve_pattern_blocks( $blocks_to_insert );
+			$inner_content      = $prev_inner_content;
+			unset( $seen_refs[ $slug ] );
+			array_splice( $blocks, $i, 1, $blocks_to_insert );
+
+			// If we have inner content, we need to insert nulls in the
+			// inner content array, otherwise serialize_blocks will skip
+			// blocks.
+			if ( $inner_content ) {
+				$null_indices  = array_keys( $inner_content, null, true );
+				$content_index = $null_indices[ $i ];
+				$nulls         = array_fill( 0, count( $blocks_to_insert ), null );
+				array_splice( $inner_content, $content_index, 1, $nulls );
+			}
+
+			// Skip inserted blocks.
+			$i += count( $blocks_to_insert );
+		} else {
+			if ( ! empty( $blocks[ $i ]['innerBlocks'] ) ) {
+				$prev_inner_content           = $inner_content;
+				$inner_content                = $blocks[ $i ]['innerContent'];
+				$blocks[ $i ]['innerBlocks']  = resolve_pattern_blocks(
+					$blocks[ $i ]['innerBlocks']
+				);
+				$blocks[ $i ]['innerContent'] = $inner_content;
+				$inner_content                = $prev_inner_content;
+			}
+			++$i;
+		}
+	}
+	return $blocks;
+}
+
+/**
+ * Given an array of parsed block trees, applies callbacks before and after serializing them and
+ * returns their concatenated output.
+ *
+ * Recursively traverses the blocks and their inner blocks and applies the two callbacks provided as
+ * arguments, the first one before serializing a block, and the second one after serializing.
+ * If either callback returns a string value, it will be prepended and appended to the serialized
+ * block markup, respectively.
+ *
+ * The callbacks will receive a reference to the current block as their first argument, so that they
+ * can also modify it, and the current block's parent block as second argument. Finally, the
+ * `$pre_callback` receives the previous block, whereas the `$post_callback` receives
+ * the next block as third argument.
+ *
+ * Serialized blocks are returned including comment delimiters, and with all attributes serialized.
+ *
+ * This function should be used when there is a need to modify the saved blocks, or to inject markup
+ * into the return value. Prefer `serialize_blocks` when preparing blocks to be saved to post content.
+ *
+ * This function is meant for internal use only.
+ *
+ * @since 6.4.0
+ * @access private
+ *
+ * @see serialize_blocks()
+ *
+ * @param array[]  $blocks        An array of parsed blocks. See WP_Block_Parser_Block.
+ * @param callable $pre_callback  Callback to run on each block in the tree before it is traversed and serialized.
+ *                                It is called with the following arguments: &$block, $parent_block, $previous_block.
+ *                                Its string return value will be prepended to the serialized block markup.
+ * @param callable $post_callback Callback to run on each block in the tree after it is traversed and serialized.
+ *                                It is called with the following arguments: &$block, $parent_block, $next_block.
+ *                                Its string return value will be appended to the serialized block markup.
+ * @return string Serialized block markup.
+ */
+function traverse_and_serialize_blocks( $blocks, $pre_callback = null, $post_callback = null ) {
+	$result       = '';
+	$parent_block = null; // At the top level, there is no parent block to pass to the callbacks; yet the callbacks expect a reference.
+
+	foreach ( $blocks as $index => $block ) {
+		if ( is_callable( $pre_callback ) ) {
+			$prev = 0 === $index
+				? null
+				: $blocks[ $index - 1 ];
+
+			$result .= call_user_func_array(
+				$pre_callback,
+				array( &$block, &$parent_block, $prev )
+			);
+		}
+
+		if ( is_callable( $post_callback ) ) {
+			$next = count( $blocks ) - 1 === $index
+				? null
+				: $blocks[ $index + 1 ];
+
+			$post_markup = call_user_func_array(
+				$post_callback,
+				array( &$block, &$parent_block, $next )
+			);
+		}
+
+		$result .= traverse_and_serialize_block( $block, $pre_callback, $post_callback );
+		$result .= isset( $post_markup ) ? $post_markup : '';
+	}
+
+	return $result;
+}
+
+/**
+ * Filters and sanitizes block content to remove non-allowable HTML
+ * from parsed block attribute values.
  *
  * @since 5.3.1
  *
  * @param string         $text              Text that may contain block content.
- * @param array[]|string $allowed_html      An array of allowed HTML elements
- *                                          and attributes, or a context name
- *                                          such as 'post'.
- * @param string[]       $allowed_protocols Array of allowed URL protocols.
+ * @param array[]|string $allowed_html      Optional. An array of allowed HTML elements and attributes,
+ *                                          or a context name such as 'post'. See wp_kses_allowed_html()
+ *                                          for the list of accepted context names. Default 'post'.
+ * @param string[]       $allowed_protocols Optional. Array of allowed URL protocols.
+ *                                          Defaults to the result of wp_allowed_protocols().
  * @return string The filtered and sanitized content result.
  */
 function filter_block_content( $text, $allowed_html = 'post', $allowed_protocols = array() ) {
 	$result = '';
 
+	if ( str_contains( $text, '<!--' ) && str_contains( $text, '--->' ) ) {
+		$text = preg_replace_callback( '%<!--(.*?)--->%', '_filter_block_content_callback', $text );
+	}
+
 	$blocks = parse_blocks( $text );
 	foreach ( $blocks as $block ) {
 		$block   = filter_block_kses( $block, $allowed_html, $allowed_protocols );
@@ -657,20 +1698,34 @@
 }
 
 /**
- * Filters and sanitizes a parsed block to remove non-allowable HTML from block
- * attribute values.
+ * Callback used for regular expression replacement in filter_block_content().
+ *
+ * @since 6.2.1
+ * @access private
+ *
+ * @param array $matches Array of preg_replace_callback matches.
+ * @return string Replacement string.
+ */
+function _filter_block_content_callback( $matches ) {
+	return '<!--' . rtrim( $matches[1], '-' ) . '-->';
+}
+
+/**
+ * Filters and sanitizes a parsed block to remove non-allowable HTML
+ * from block attribute values.
  *
  * @since 5.3.1
  *
  * @param WP_Block_Parser_Block $block             The parsed block object.
- * @param array[]|string        $allowed_html      An array of allowed HTML
- *                                                 elements and attributes, or a
- *                                                 context name such as 'post'.
- * @param string[]              $allowed_protocols Allowed URL protocols.
+ * @param array[]|string        $allowed_html      An array of allowed HTML elements and attributes,
+ *                                                 or a context name such as 'post'. See wp_kses_allowed_html()
+ *                                                 for the list of accepted context names.
+ * @param string[]              $allowed_protocols Optional. Array of allowed URL protocols.
+ *                                                 Defaults to the result of wp_allowed_protocols().
  * @return array The filtered and sanitized block object result.
  */
 function filter_block_kses( $block, $allowed_html, $allowed_protocols = array() ) {
-	$block['attrs'] = filter_block_kses_value( $block['attrs'], $allowed_html, $allowed_protocols );
+	$block['attrs'] = filter_block_kses_value( $block['attrs'], $allowed_html, $allowed_protocols, $block );
 
 	if ( is_array( $block['innerBlocks'] ) ) {
 		foreach ( $block['innerBlocks'] as $i => $inner_block ) {
@@ -682,24 +1737,30 @@
 }
 
 /**
- * Filters and sanitizes a parsed block attribute value to remove non-allowable
- * HTML.
+ * Filters and sanitizes a parsed block attribute value to remove
+ * non-allowable HTML.
  *
  * @since 5.3.1
+ * @since 6.5.5 Added the `$block_context` parameter.
  *
  * @param string[]|string $value             The attribute value to filter.
- * @param array[]|string  $allowed_html      An array of allowed HTML elements
- *                                           and attributes, or a context name
- *                                           such as 'post'.
- * @param string[]        $allowed_protocols Array of allowed URL protocols.
+ * @param array[]|string  $allowed_html      An array of allowed HTML elements and attributes,
+ *                                           or a context name such as 'post'. See wp_kses_allowed_html()
+ *                                           for the list of accepted context names.
+ * @param string[]        $allowed_protocols Optional. Array of allowed URL protocols.
+ *                                           Defaults to the result of wp_allowed_protocols().
+ * @param array           $block_context     Optional. The block the attribute belongs to, in parsed block array format.
  * @return string[]|string The filtered and sanitized result.
  */
-function filter_block_kses_value( $value, $allowed_html, $allowed_protocols = array() ) {
+function filter_block_kses_value( $value, $allowed_html, $allowed_protocols = array(), $block_context = null ) {
 	if ( is_array( $value ) ) {
 		foreach ( $value as $key => $inner_value ) {
-			$filtered_key   = filter_block_kses_value( $key, $allowed_html, $allowed_protocols );
-			$filtered_value = filter_block_kses_value( $inner_value, $allowed_html, $allowed_protocols );
+			$filtered_key   = filter_block_kses_value( $key, $allowed_html, $allowed_protocols, $block_context );
+			$filtered_value = filter_block_kses_value( $inner_value, $allowed_html, $allowed_protocols, $block_context );
 
+			if ( isset( $block_context['blockName'] ) && 'core/template-part' === $block_context['blockName'] ) {
+				$filtered_value = filter_block_core_template_part_attributes( $filtered_value, $filtered_key, $allowed_html );
+			}
 			if ( $filtered_key !== $key ) {
 				unset( $value[ $key ] );
 			}
@@ -714,6 +1775,28 @@
 }
 
 /**
+ * Sanitizes the value of the Template Part block's `tagName` attribute.
+ *
+ * @since 6.5.5
+ *
+ * @param string         $attribute_value The attribute value to filter.
+ * @param string         $attribute_name  The attribute name.
+ * @param array[]|string $allowed_html    An array of allowed HTML elements and attributes,
+ *                                        or a context name such as 'post'. See wp_kses_allowed_html()
+ *                                        for the list of accepted context names.
+ * @return string The sanitized attribute value.
+ */
+function filter_block_core_template_part_attributes( $attribute_value, $attribute_name, $allowed_html ) {
+	if ( empty( $attribute_value ) || 'tagName' !== $attribute_name ) {
+		return $attribute_value;
+	}
+	if ( ! is_array( $allowed_html ) ) {
+		$allowed_html = wp_kses_allowed_html( $allowed_html );
+	}
+	return isset( $allowed_html[ $attribute_value ] ) ? $attribute_value : '';
+}
+
+/**
  * Parses blocks out of a content string, and renders those appropriate for the excerpt.
  *
  * As the excerpt should be a small string of text relevant to the full post content,
@@ -725,6 +1808,10 @@
  * @return string The parsed and filtered content.
  */
 function excerpt_remove_blocks( $content ) {
+	if ( ! has_blocks( $content ) ) {
+		return $content;
+	}
+
 	$allowed_inner_blocks = array(
 		// Classic blocks have their blockName set to null.
 		null,
@@ -800,7 +1887,28 @@
 }
 
 /**
- * Render inner blocks from the allowed wrapper blocks
+ * Parses footnotes markup out of a content string,
+ * and renders those appropriate for the excerpt.
+ *
+ * @since 6.3.0
+ *
+ * @param string $content The content to parse.
+ * @return string The parsed and filtered content.
+ */
+function excerpt_remove_footnotes( $content ) {
+	if ( ! str_contains( $content, 'data-fn=' ) ) {
+		return $content;
+	}
+
+	return preg_replace(
+		'_<sup data-fn="[^"]+" class="[^"]+">\s*<a href="[^"]+" id="[^"]+">\d+</a>\s*</sup>_',
+		'',
+		$content
+	);
+}
+
+/**
+ * Renders inner blocks from the allowed wrapper blocks
  * for generating an excerpt.
  *
  * @since 5.8.0
@@ -833,9 +1941,19 @@
  *
  * @since 5.0.0
  *
- * @global WP_Post  $post     The post to edit.
+ * @global WP_Post $post The post to edit.
+ *
+ * @param array $parsed_block {
+ *     A representative array of the block being rendered. See WP_Block_Parser_Block.
  *
- * @param array $parsed_block A single parsed block object.
+ *     @type string   $blockName    Name of block.
+ *     @type array    $attrs        Attributes from block comment delimiters.
+ *     @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+ *                                  have the same structure as this one.
+ *     @type string   $innerHTML    HTML from inside block comment delimiters.
+ *     @type array    $innerContent List of string fragments and null markers where
+ *                                  inner blocks were found.
+ * }
  * @return string String of rendered HTML.
  */
 function render_block( $parsed_block ) {
@@ -849,7 +1967,17 @@
 	 * @since 5.9.0 The `$parent_block` parameter was added.
 	 *
 	 * @param string|null   $pre_render   The pre-rendered content. Default null.
-	 * @param array         $parsed_block The block being rendered.
+	 * @param array         $parsed_block {
+	 *     A representative array of the block being rendered. See WP_Block_Parser_Block.
+	 *
+	 *     @type string   $blockName    Name of block.
+	 *     @type array    $attrs        Attributes from block comment delimiters.
+	 *     @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+	 *                                  have the same structure as this one.
+	 *     @type string   $innerHTML    HTML from inside block comment delimiters.
+	 *     @type array    $innerContent List of string fragments and null markers where
+	 *                                  inner blocks were found.
+	 * }
 	 * @param WP_Block|null $parent_block If this is a nested block, a reference to the parent block.
 	 */
 	$pre_render = apply_filters( 'pre_render_block', null, $parsed_block, $parent_block );
@@ -865,8 +1993,29 @@
 	 * @since 5.1.0
 	 * @since 5.9.0 The `$parent_block` parameter was added.
 	 *
-	 * @param array         $parsed_block The block being rendered.
-	 * @param array         $source_block An un-modified copy of $parsed_block, as it appeared in the source content.
+	 * @param array         $parsed_block {
+	 *     A representative array of the block being rendered. See WP_Block_Parser_Block.
+	 *
+	 *     @type string   $blockName    Name of block.
+	 *     @type array    $attrs        Attributes from block comment delimiters.
+	 *     @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+	 *                                  have the same structure as this one.
+	 *     @type string   $innerHTML    HTML from inside block comment delimiters.
+	 *     @type array    $innerContent List of string fragments and null markers where
+	 *                                  inner blocks were found.
+	 * }
+	 * @param array         $source_block {
+	 *     An un-modified copy of `$parsed_block`, as it appeared in the source content.
+	 *     See WP_Block_Parser_Block.
+	 *
+	 *     @type string   $blockName    Name of block.
+	 *     @type array    $attrs        Attributes from block comment delimiters.
+	 *     @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+	 *                                  have the same structure as this one.
+	 *     @type string   $innerHTML    HTML from inside block comment delimiters.
+	 *     @type array    $innerContent List of string fragments and null markers where
+	 *                                  inner blocks were found.
+	 * }
 	 * @param WP_Block|null $parent_block If this is a nested block, a reference to the parent block.
 	 */
 	$parsed_block = apply_filters( 'render_block_data', $parsed_block, $source_block, $parent_block );
@@ -892,7 +2041,17 @@
 	 * @since 5.9.0 The `$parent_block` parameter was added.
 	 *
 	 * @param array         $context      Default context.
-	 * @param array         $parsed_block Block being rendered, filtered by `render_block_data`.
+	 * @param array         $parsed_block {
+	 *     A representative array of the block being rendered. See WP_Block_Parser_Block.
+	 *
+	 *     @type string   $blockName    Name of block.
+	 *     @type array    $attrs        Attributes from block comment delimiters.
+	 *     @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+	 *                                  have the same structure as this one.
+	 *     @type string   $innerHTML    HTML from inside block comment delimiters.
+	 *     @type array    $innerContent List of string fragments and null markers where
+	 *                                  inner blocks were found.
+	 * }
 	 * @param WP_Block|null $parent_block If this is a nested block, a reference to the parent block.
 	 */
 	$context = apply_filters( 'render_block_context', $context, $parsed_block, $parent_block );
@@ -908,11 +2067,25 @@
  * @since 5.0.0
  *
  * @param string $content Post content.
- * @return array[] Array of parsed block objects.
+ * @return array[] {
+ *     Array of block structures.
+ *
+ *     @type array ...$0 {
+ *         A representative array of a single parsed block object. See WP_Block_Parser_Block.
+ *
+ *         @type string   $blockName    Name of block.
+ *         @type array    $attrs        Attributes from block comment delimiters.
+ *         @type array[]  $innerBlocks  List of inner blocks. An array of arrays that
+ *                                      have the same structure as this one.
+ *         @type string   $innerHTML    HTML from inside block comment delimiters.
+ *         @type array    $innerContent List of string fragments and null markers where
+ *                                      inner blocks were found.
+ *     }
+ * }
  */
 function parse_blocks( $content ) {
 	/**
-	 * Filter to allow plugins to replace the server-side block parser
+	 * Filter to allow plugins to replace the server-side block parser.
 	 *
 	 * @since 5.0.0
 	 *
@@ -987,11 +2160,16 @@
  * Registers a new block style.
  *
  * @since 5.3.0
+ * @since 6.6.0 Added support for registering styles for multiple block types.
  *
- * @param string $block_name       Block type name including namespace.
- * @param array  $style_properties Array containing the properties of the style name,
- *                                 label, style (name of the stylesheet to be enqueued),
- *                                 inline_style (string containing the CSS to be added).
+ * @link https://developer.wordpress.org/block-editor/reference-guides/block-api/block-styles/
+ *
+ * @param string|string[] $block_name       Block type name including namespace or array of namespaced block type names.
+ * @param array           $style_properties Array containing the properties of the style name, label,
+ *                                          style_handle (name of the stylesheet to be enqueued),
+ *                                          inline_style (string containing the CSS to be added),
+ *                                          style_data (theme.json-like array to generate CSS from).
+ *                                          See WP_Block_Styles_Registry::register().
  * @return bool True if the block style was registered with success and false otherwise.
  */
 function register_block_style( $block_name, $style_properties ) {
@@ -1015,16 +2193,25 @@
  * Checks whether the current block type supports the feature requested.
  *
  * @since 5.8.0
+ * @since 6.4.0 The `$feature` parameter now supports a string.
  *
- * @param WP_Block_Type $block_type Block type to check for support.
- * @param string        $feature    Name of the feature to check support for.
- * @param mixed         $default    Optional. Fallback value for feature support. Default false.
+ * @param WP_Block_Type $block_type    Block type to check for support.
+ * @param string|array  $feature       Feature slug, or path to a specific feature to check support for.
+ * @param mixed         $default_value Optional. Fallback value for feature support. Default false.
  * @return bool Whether the feature is supported.
  */
-function block_has_support( $block_type, $feature, $default = false ) {
-	$block_support = $default;
-	if ( $block_type && property_exists( $block_type, 'supports' ) ) {
-		$block_support = _wp_array_get( $block_type->supports, $feature, $default );
+function block_has_support( $block_type, $feature, $default_value = false ) {
+	$block_support = $default_value;
+	if ( $block_type instanceof WP_Block_Type ) {
+		if ( is_array( $feature ) && count( $feature ) === 1 ) {
+			$feature = $feature[0];
+		}
+
+		if ( is_array( $feature ) ) {
+			$block_support = _wp_array_get( $block_type->supports, $feature, $default_value );
+		} elseif ( isset( $block_type->supports[ $feature ] ) ) {
+			$block_support = $block_type->supports[ $feature ];
+		}
 	}
 
 	return true === $block_support || is_array( $block_support );
@@ -1057,7 +2244,7 @@
 	);
 
 	foreach ( $typography_keys as $typography_key ) {
-		$support_for_key = _wp_array_get( $metadata['supports'], array( $typography_key ), null );
+		$support_for_key = isset( $metadata['supports'][ $typography_key ] ) ? $metadata['supports'][ $typography_key ] : null;
 
 		if ( null !== $support_for_key ) {
 			_doing_it_wrong(
@@ -1089,6 +2276,7 @@
  * It's used in Query Loop, Query Pagination Numbers and Query Pagination Next blocks.
  *
  * @since 5.8.0
+ * @since 6.1.0 Added `query_loop_block_query_vars` filter and `parents` support in query.
  *
  * @param WP_Block $block Block instance.
  * @param int      $page  Current query's page.
@@ -1113,7 +2301,15 @@
 		if ( isset( $block->context['query']['sticky'] ) && ! empty( $block->context['query']['sticky'] ) ) {
 			$sticky = get_option( 'sticky_posts' );
 			if ( 'only' === $block->context['query']['sticky'] ) {
-				$query['post__in'] = $sticky;
+				/*
+				 * Passing an empty array to post__in will return have_posts() as true (and all posts will be returned).
+				 * Logic should be used before hand to determine if WP_Query should be used in the event that the array
+				 * being passed to post__in is empty.
+				 *
+				 * @see https://core.trac.wordpress.org/ticket/28099
+				 */
+				$query['post__in']            = ! empty( $sticky ) ? $sticky : array( 0 );
+				$query['ignore_sticky_posts'] = 1;
 			} else {
 				$query['post__not_in'] = array_merge( $query['post__not_in'], $sticky );
 			}
@@ -1181,16 +2377,45 @@
 			$query['orderby'] = $block->context['query']['orderBy'];
 		}
 		if (
-			isset( $block->context['query']['author'] ) &&
-			(int) $block->context['query']['author'] > 0
+			isset( $block->context['query']['author'] )
 		) {
-			$query['author'] = (int) $block->context['query']['author'];
+			if ( is_array( $block->context['query']['author'] ) ) {
+				$query['author__in'] = array_filter( array_map( 'intval', $block->context['query']['author'] ) );
+			} elseif ( is_string( $block->context['query']['author'] ) ) {
+				$query['author__in'] = array_filter( array_map( 'intval', explode( ',', $block->context['query']['author'] ) ) );
+			} elseif ( is_int( $block->context['query']['author'] ) && $block->context['query']['author'] > 0 ) {
+				$query['author'] = $block->context['query']['author'];
+			}
 		}
 		if ( ! empty( $block->context['query']['search'] ) ) {
 			$query['s'] = $block->context['query']['search'];
 		}
+		if ( ! empty( $block->context['query']['parents'] ) && is_post_type_hierarchical( $query['post_type'] ) ) {
+			$query['post_parent__in'] = array_filter( array_map( 'intval', $block->context['query']['parents'] ) );
+		}
 	}
-	return $query;
+
+	/**
+	 * Filters the arguments which will be passed to `WP_Query` for the Query Loop Block.
+	 *
+	 * Anything to this filter should be compatible with the `WP_Query` API to form
+	 * the query context which will be passed down to the Query Loop Block's children.
+	 * This can help, for example, to include additional settings or meta queries not
+	 * directly supported by the core Query Loop Block, and extend its capabilities.
+	 *
+	 * Please note that this will only influence the query that will be rendered on the
+	 * front-end. The editor preview is not affected by this filter. Also, worth noting
+	 * that the editor preview uses the REST API, so, ideally, one should aim to provide
+	 * attributes which are also compatible with the REST API, in order to be able to
+	 * implement identical queries on both sides.
+	 *
+	 * @since 6.1.0
+	 *
+	 * @param array    $query Array containing parameters for `WP_Query` as parsed by the block context.
+	 * @param WP_Block $block Block instance.
+	 * @param int      $page  Current query's page.
+	 */
+	return apply_filters( 'query_loop_block_query_vars', $query, $block, $page );
 }
 
 /**
@@ -1203,8 +2428,7 @@
  * @since 5.9.0
  *
  * @param WP_Block $block   Block instance.
- * @param boolean  $is_next Flag for handling `next/previous` blocks.
- *
+ * @param bool     $is_next Flag for handling `next/previous` blocks.
  * @return string|null The pagination arrow HTML or null if there is none.
  */
 function get_query_pagination_arrow( $block, $is_next ) {
@@ -1224,55 +2448,12 @@
 		$arrow_attribute = $block->context['paginationArrow'];
 		$arrow           = $arrow_map[ $block->context['paginationArrow'] ][ $pagination_type ];
 		$arrow_classes   = "wp-block-query-pagination-$pagination_type-arrow is-arrow-$arrow_attribute";
-		return "<span class='$arrow_classes'>$arrow</span>";
+		return "<span class='$arrow_classes' aria-hidden='true'>$arrow</span>";
 	}
 	return null;
 }
 
 /**
- * Allows multiple block styles.
- *
- * @since 5.9.0
- *
- * @param array $metadata Metadata for registering a block type.
- * @return array Metadata for registering a block type.
- */
-function _wp_multiple_block_styles( $metadata ) {
-	foreach ( array( 'style', 'editorStyle' ) as $key ) {
-		if ( ! empty( $metadata[ $key ] ) && is_array( $metadata[ $key ] ) ) {
-			$default_style = array_shift( $metadata[ $key ] );
-			foreach ( $metadata[ $key ] as $handle ) {
-				$args = array( 'handle' => $handle );
-				if ( 0 === strpos( $handle, 'file:' ) && isset( $metadata['file'] ) ) {
-					$style_path      = remove_block_asset_path_prefix( $handle );
-					$theme_path_norm = wp_normalize_path( get_theme_file_path() );
-					$style_path_norm = wp_normalize_path( realpath( dirname( $metadata['file'] ) . '/' . $style_path ) );
-					$is_theme_block  = isset( $metadata['file'] ) && 0 === strpos( $metadata['file'], $theme_path_norm );
-
-					$style_uri = plugins_url( $style_path, $metadata['file'] );
-
-					if ( $is_theme_block ) {
-						$style_uri = get_theme_file_uri( str_replace( $theme_path_norm, '', $style_path_norm ) );
-					}
-
-					$args = array(
-						'handle' => sanitize_key( "{$metadata['name']}-{$style_path}" ),
-						'src'    => $style_uri,
-					);
-				}
-
-				wp_enqueue_block_style( $metadata['name'], $args );
-			}
-
-			// Only return the 1st item in the array.
-			$metadata[ $key ] = $default_style;
-		}
-	}
-	return $metadata;
-}
-add_filter( 'block_type_metadata', '_wp_multiple_block_styles' );
-
-/**
  * Helper function that constructs a comment query vars array from the passed
  * block properties.
  *
@@ -1281,7 +2462,6 @@
  * @since 6.0.0
  *
  * @param WP_Block $block Block instance.
- *
  * @return array Returns the comment query parameters to use with the
  *               WP_Comment_Query constructor.
  */
@@ -1352,9 +2532,8 @@
  * @since 6.0.0
  *
  * @param WP_Block $block           Block instance.
- * @param string   $pagination_type Type of the arrow we will be rendering.
- *                                  Default 'next'. Accepts 'next' or 'previous'.
- *
+ * @param string   $pagination_type Optional. Type of the arrow we will be rendering.
+ *                                  Accepts 'next' or 'previous'. Default 'next'.
  * @return string|null The pagination arrow HTML or null if there is none.
  */
 function get_comments_pagination_arrow( $block, $pagination_type = 'next' ) {
@@ -1373,7 +2552,90 @@
 		$arrow_attribute = $block->context['comments/paginationArrow'];
 		$arrow           = $arrow_map[ $block->context['comments/paginationArrow'] ][ $pagination_type ];
 		$arrow_classes   = "wp-block-comments-pagination-$pagination_type-arrow is-arrow-$arrow_attribute";
-		return "<span class='$arrow_classes'>$arrow</span>";
+		return "<span class='$arrow_classes' aria-hidden='true'>$arrow</span>";
 	}
 	return null;
 }
+
+/**
+ * Strips all HTML from the content of footnotes, and sanitizes the ID.
+ *
+ * This function expects slashed data on the footnotes content.
+ *
+ * @access private
+ * @since 6.3.2
+ *
+ * @param string $footnotes JSON-encoded string of an array containing the content and ID of each footnote.
+ * @return string Filtered content without any HTML on the footnote content and with the sanitized ID.
+ */
+function _wp_filter_post_meta_footnotes( $footnotes ) {
+	$footnotes_decoded = json_decode( $footnotes, true );
+	if ( ! is_array( $footnotes_decoded ) ) {
+		return '';
+	}
+	$footnotes_sanitized = array();
+	foreach ( $footnotes_decoded as $footnote ) {
+		if ( ! empty( $footnote['content'] ) && ! empty( $footnote['id'] ) ) {
+			$footnotes_sanitized[] = array(
+				'id'      => sanitize_key( $footnote['id'] ),
+				'content' => wp_unslash( wp_filter_post_kses( wp_slash( $footnote['content'] ) ) ),
+			);
+		}
+	}
+	return wp_json_encode( $footnotes_sanitized );
+}
+
+/**
+ * Adds the filters for footnotes meta field.
+ *
+ * @access private
+ * @since 6.3.2
+ */
+function _wp_footnotes_kses_init_filters() {
+	add_filter( 'sanitize_post_meta_footnotes', '_wp_filter_post_meta_footnotes' );
+}
+
+/**
+ * Removes the filters for footnotes meta field.
+ *
+ * @access private
+ * @since 6.3.2
+ */
+function _wp_footnotes_remove_filters() {
+	remove_filter( 'sanitize_post_meta_footnotes', '_wp_filter_post_meta_footnotes' );
+}
+
+/**
+ * Registers the filter of footnotes meta field if the user does not have `unfiltered_html` capability.
+ *
+ * @access private
+ * @since 6.3.2
+ */
+function _wp_footnotes_kses_init() {
+	_wp_footnotes_remove_filters();
+	if ( ! current_user_can( 'unfiltered_html' ) ) {
+		_wp_footnotes_kses_init_filters();
+	}
+}
+
+/**
+ * Initializes the filters for footnotes meta field when imported data should be filtered.
+ *
+ * This filter is the last one being executed on {@see 'force_filtered_html_on_import'}.
+ * If the input of the filter is true, it means we are in an import situation and should
+ * enable kses, independently of the user capabilities. So in that case we call
+ * _wp_footnotes_kses_init_filters().
+ *
+ * @access private
+ * @since 6.3.2
+ *
+ * @param string $arg Input argument of the filter.
+ * @return string Input argument of the filter.
+ */
+function _wp_footnotes_force_filtered_html_on_import_filter( $arg ) {
+	// If `force_filtered_html_on_import` is true, we need to init the global styles kses filters.
+	if ( $arg ) {
+		_wp_footnotes_kses_init_filters();
+	}
+	return $arg;
+}