Ticket #41488: 41488.3.diff

src/wp-includes/class-wp-customize-nav-menus.php

@@ -1265 +1265 @@
          *
          * @param string $nav_menu_content The HTML content for the navigation menu.
          * @param object $args             An object containing wp_nav_menu() arguments.
-         * @return null
+         * @return string Updated HTML content.
          */
         public function filter_wp_nav_menu( $nav_menu_content, $args ) {
                 if ( isset( $args->customize_preview_nav_menus_args['can_partial_refresh'] ) && $args->customize_preview_nav_menus_args['can_partial_refresh'] ) {
                         $attributes = sprintf( ' data-customize-partial-id="%s"', esc_attr( 'nav_menu_instance[' . $args->customize_preview_nav_menus_args['args_hmac'] . ']' ) );
                         $attributes .= ' data-customize-partial-type="nav_menu_instance"';
                         $attributes .= sprintf( ' data-customize-partial-placement-context="%s"', esc_attr( wp_json_encode( $args->customize_preview_nav_menus_args ) ) );
-                        $nav_menu_content = preg_replace( '#^(<\w+)#', '$1 ' . $attributes, $nav_menu_content, 1 );
+                        $nav_menu_content = preg_replace( '#^(<\w+)#', '$1 ' . preg_quote( $attributes, '#' ), $nav_menu_content, 1 );
                 }
+
                 return $nav_menu_content;
         }