KSES: Add `object-position` to the list of safe CSS properties.

This resolves an issue with the Cover block, where the `object-position` property is removed from the content when a non-admin user saves the post, leading to block recovery loop.

Props Mamaduka, aristath.
Merges [50634] to the 5.7 branch.
Fixes #52961.
Built from https://develop.svn.wordpress.org/branches/5.7@50649


git-svn-id: http://core.svn.wordpress.org/branches/5.7@50261 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/kses.php

@@ -2171,6 +2171,7 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 	 * @since 5.3.0 Added support for `grid`, `flex` and `column` layout properties.
 	 *              Extend `background-*` support of individual properties.
 	 * @since 5.3.1 Added support for gradient backgrounds.
+	 * @since 5.7.1 Added support for `object-position`.
 	 *
 	 * @param string[] $attr Array of allowed CSS attributes.
 	 */
@@ -2284,6 +2285,7 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 			'direction',
 			'float',
 			'list-style-type',
+			'object-position',
 			'overflow',
 			'vertical-align',
 		)

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7.1-alpha-50630';
+$wp_version = '5.7.1-alpha-50649';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.