diff -r 3d4e9c994f10 -r a86126ab1dd4 wp/wp-includes/class-wp-oembed-controller.php
--- a/wp/wp-includes/class-wp-oembed-controller.php	Tue Oct 22 16:11:46 2019 +0200
+++ b/wp/wp-includes/class-wp-oembed-controller.php	Tue Dec 15 13:49:49 2020 +0100
@@ -36,12 +36,15 @@
 			'/embed',
 			array(
 				array(
-					'methods'  => WP_REST_Server::READABLE,
-					'callback' => array( $this, 'get_item' ),
-					'args'     => array(
+					'methods'             => WP_REST_Server::READABLE,
+					'callback'            => array( $this, 'get_item' ),
+					'permission_callback' => '__return_true',
+					'args'                => array(
 						'url'      => array(
-							'required'          => true,
-							'sanitize_callback' => 'esc_url_raw',
+							'description' => __( 'The URL of the resource for which to fetch oEmbed data.' ),
+							'required'    => true,
+							'type'        => 'string',
+							'format'      => 'uri',
 						),
 						'format'   => array(
 							'default'           => 'json',
@@ -66,10 +69,10 @@
 					'permission_callback' => array( $this, 'get_proxy_item_permissions_check' ),
 					'args'                => array(
 						'url'       => array(
-							'description'       => __( 'The URL of the resource for which to fetch oEmbed data.' ),
-							'type'              => 'string',
-							'required'          => true,
-							'sanitize_callback' => 'esc_url_raw',
+							'description' => __( 'The URL of the resource for which to fetch oEmbed data.' ),
+							'required'    => true,
+							'type'        => 'string',
+							'format'      => 'uri',
 						),
 						'format'    => array(
 							'description' => __( 'The oEmbed format to use.' ),
@@ -92,7 +95,7 @@
 							'sanitize_callback' => 'absint',
 						),
 						'discover'  => array(
-							'description' => __( 'Whether to perform an oEmbed discovery request for non-whitelisted providers.' ),
+							'description' => __( 'Whether to perform an oEmbed discovery request for unsanctioned providers.' ),
 							'type'        => 'boolean',
 							'default'     => true,
 						),
@@ -110,7 +113,7 @@
 	 * @since 4.4.0
 	 *
 	 * @param WP_REST_Request $request Full data about the request.
-	 * @return WP_Error|array oEmbed response data or WP_Error on failure.
+	 * @return array|WP_Error oEmbed response data or WP_Error on failure.
 	 */
 	public function get_item( $request ) {
 		$post_id = url_to_postid( $request['url'] );
@@ -191,10 +194,32 @@
 		$data = _wp_oembed_get_object()->get_data( $url, $args );
 
 		if ( false === $data ) {
+			// Try using a classic embed, instead.
+			global $wp_embed;
+
+			/* @var WP_Embed $wp_embed */
+			$html = $wp_embed->get_embed_handler_html( $args, $url );
+
+			if ( $html ) {
+				global $wp_scripts;
+				// Check if any scripts were enqueued by the shortcode, and include them in the response.
+				$enqueued_scripts = array();
+
+				foreach ( $wp_scripts->queue as $script ) {
+					$enqueued_scripts[] = $wp_scripts->registered[ $script ]->src;
+				}
+
+				return (object) array(
+					'provider_name' => __( 'Embed Handler' ),
+					'html'          => $html,
+					'scripts'       => $enqueued_scripts,
+				);
+			}
+
 			return new WP_Error( 'oembed_invalid_url', get_status_header_desc( 404 ), array( 'status' => 404 ) );
 		}
 
-		/** This filter is documented in wp-includes/class-oembed.php */
+		/** This filter is documented in wp-includes/class-wp-oembed.php */
 		$data->html = apply_filters( 'oembed_result', _wp_oembed_get_object()->data2html( (object) $data, $url ), $url, $args );
 
 		/**