diff -r be944660c56a -r 3d72ae0968f4 wp/wp-includes/blocks/widget-group.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/blocks/widget-group.php	Tue Sep 27 16:37:53 2022 +0200
@@ -0,0 +1,78 @@
+<?php
+/**
+ * Server-side rendering of the `core/widget-group` block.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Renders the 'core/widget-group' block.
+ *
+ * @param array    $attributes The block attributes.
+ * @param string   $content The block content.
+ * @param WP_Block $block The block.
+ *
+ * @return string Rendered block.
+ */
+function render_block_core_widget_group( $attributes, $content, $block ) {
+	global $wp_registered_sidebars, $_sidebar_being_rendered;
+
+	if ( isset( $wp_registered_sidebars[ $_sidebar_being_rendered ] ) ) {
+		$before_title = $wp_registered_sidebars[ $_sidebar_being_rendered ]['before_title'];
+		$after_title  = $wp_registered_sidebars[ $_sidebar_being_rendered ]['after_title'];
+	} else {
+		$before_title = '<h2 class="widget-title">';
+		$after_title  = '</h2>';
+	}
+
+	$html = '';
+
+	if ( ! empty( $attributes['title'] ) ) {
+		$html .= $before_title . $attributes['title'] . $after_title;
+	}
+
+	$html .= '<div class="wp-widget-group__inner-blocks">';
+	foreach ( $block->inner_blocks as $inner_block ) {
+		$html .= $inner_block->render();
+	}
+	$html .= '</div>';
+
+	return $html;
+}
+
+/**
+ * Registers the 'core/widget-group' block.
+ */
+function register_block_core_widget_group() {
+	register_block_type_from_metadata(
+		__DIR__ . '/widget-group',
+		array(
+			'render_callback' => 'render_block_core_widget_group',
+		)
+	);
+}
+
+add_action( 'init', 'register_block_core_widget_group' );
+
+/**
+ * Make a note of the sidebar being rendered before WordPress starts rendering
+ * it. This lets us get to the current sidebar in
+ * render_block_core_widget_group().
+ *
+ * @param int|string $index       Index, name, or ID of the dynamic sidebar.
+ */
+function note_sidebar_being_rendered( $index ) {
+	global $_sidebar_being_rendered;
+	$_sidebar_being_rendered = $index;
+}
+add_action( 'dynamic_sidebar_before', 'note_sidebar_being_rendered' );
+
+/**
+ * Clear whatever we set in note_sidebar_being_rendered() after WordPress
+ * finishes rendering a sidebar.
+ */
+function discard_sidebar_being_rendered() {
+	global $_sidebar_being_rendered;
+	unset( $_sidebar_being_rendered );
+}
+add_action( 'dynamic_sidebar_after', 'discard_sidebar_being_rendered' );