diff --git src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php
index cbc3dc4c90..d14119133a 100644
--- src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php
+++ src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php
@@ -421,7 +421,7 @@ class WP_REST_Autosaves_Controller extends WP_REST_Revisions_Controller {
 		if ( ! empty( $meta ) ) {
 			foreach ( $revisioned_meta_keys as $meta_key ) {
 				if ( isset( $meta[ $meta_key ] ) ) {
-					update_metadata( 'post', $revision_id, $meta_key, $meta[ $meta_key ] );
+					update_metadata( 'post', $revision_id, $meta_key, wp_slash( $meta[ $meta_key ] ) );
 				}
 			}
 		}
diff --git tests/phpunit/tests/rest-api/rest-autosaves-controller.php tests/phpunit/tests/rest-api/rest-autosaves-controller.php
index 4108d05efc..c268b74518 100644
--- tests/phpunit/tests/rest-api/rest-autosaves-controller.php
+++ tests/phpunit/tests/rest-api/rest-autosaves-controller.php
@@ -341,6 +341,76 @@ class WP_Test_REST_Autosaves_Controller extends WP_Test_REST_Post_Type_Controlle
 		$this->check_create_autosave_response( $response );
 	}
 
+	public function test_update_item_with_meta() {
+		wp_set_current_user( self::$editor_id );
+		$request = new WP_REST_Request( 'POST', '/wp/v2/posts/' . self::$post_id . '/autosaves' );
+		$request->add_header( 'Content-Type', 'application/x-www-form-urlencoded' );
+		register_post_meta(
+			'post',
+			'foo',
+			array(
+				'show_in_rest'      => true,
+				'revisions_enabled' => true,
+				'single'            => true,
+			)
+		);
+		$params = $this->set_post_data(
+			array(
+				'id'     => self::$post_id,
+				'author' => self::$contributor_id,
+				'meta'   => array(
+					'foo' => 'bar',
+				),
+			)
+		);
+
+		$request->set_body_params( $params );
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->check_create_autosave_response( $response );
+
+		$data = $response->get_data();
+		$this->assertArrayHasKey( 'meta', $data );
+		$this->assertArrayHasKey( 'foo', $data['meta'] );
+		$this->assertSame( 'bar', $data['meta']['foo'] );
+	}
+
+	public function test_update_item_with_json_meta() {
+		$meta = '[{\"content\":\"foot 1\",\"id\":\"fa97a10d-7401-42b9-ac54-df8f4510749a\"},{\"content\":\"fdddddoot 2\\\"\",\"id\":\"2216d0aa-34b8-42b4-b441-84dedc0406e0\"}]';
+		wp_set_current_user( self::$editor_id );
+		$request = new WP_REST_Request( 'POST', '/wp/v2/posts/' . self::$post_id . '/autosaves' );
+		$request->add_header( 'Content-Type', 'application/x-www-form-urlencoded' );
+		register_post_meta(
+			'post',
+			'foo',
+			array(
+				'show_in_rest'      => true,
+				'revisions_enabled' => true,
+				'single'            => true,
+			)
+		);
+		$params = $this->set_post_data(
+			array(
+				'id'     => self::$post_id,
+				'author' => self::$contributor_id,
+				'meta'   => array(
+					'foo' => $meta,
+				),
+			)
+		);
+
+		$request->set_body_params( $params );
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->check_create_autosave_response( $response );
+
+		$data = $response->get_data();
+		$this->assertArrayHasKey( 'meta', $data );
+		$this->assertArrayHasKey( 'foo', $data['meta'] );
+		$values = json_decode( wp_unslash( $data['meta']['foo'] ), true );
+		$this->assertNotNull( $values );
+	}
+
 	public function test_update_item_nopriv() {
 		wp_set_current_user( self::$contributor_id );
 
diff --git tests/phpunit/tests/rest-api/rest-post-meta-fields.php tests/phpunit/tests/rest-api/rest-post-meta-fields.php
index c164c406b0..dcf39f59c9 100644
--- tests/phpunit/tests/rest-api/rest-post-meta-fields.php
+++ tests/phpunit/tests/rest-api/rest-post-meta-fields.php
@@ -3364,7 +3364,7 @@ class WP_Test_REST_Post_Meta_Fields extends WP_Test_REST_TestCase {
 	 * Test post meta revisions with a custom post type and the page post type.
 	 *
 	 * @group revision
-	 * @dataProvider test_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt_data_provider
+	 * @dataProvider data_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt_data_provider
 	 */
 	public function test_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt( $passed, $expected, $post_type ) {
 
@@ -3451,7 +3451,7 @@ class WP_Test_REST_Post_Meta_Fields extends WP_Test_REST_TestCase {
 	/**
 	 * Provide data for the meta revision checks.
 	 */
-	public function test_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt_data_provider() {
+	public function data_revisioned_single_post_meta_with_posts_endpoint_page_and_cpt_data_provider() {
 		return array(
 			array(
 				'Test string',
@@ -3468,7 +3468,6 @@ class WP_Test_REST_Post_Meta_Fields extends WP_Test_REST_TestCase {
 				false,
 				'cpt',
 			),
-
 		);
 	}
 }