Ticket #28783: 28783-2.patch

class-wp-customize-widgets.php

@@ -1138 +1138 @@
          * @return string Widget instance's hash key.
          */
         protected function get_instance_hash_key( $instance ) {
-                $hash = md5( AUTH_KEY . serialize( $instance ) );
-                return $hash;
+                return wp_hash( serialize( $instance ) );
         }
 
         /**