Ticket #47564: fix_customizer_nav_menu_freeze.diff

src/js/_enqueues/wp/customize/nav-menus.js

@@ -1876 +1876 @@
                         if ( ! setting ) {
                                 return 0;
                         }
-                        while ( setting && setting.menu_item_parent ) {
+                        // Protect against bad recursive navigation menu data causing causing browser to freeze.
+                        var seen_parents = {};
+                        while ( setting && setting.menu_item_parent && ! seen_parents[setting.menu_item_parent] ) {
                                 depth += 1;
                                 control = api.control( 'nav_menu_item[' + setting.menu_item_parent + ']' );
                                 if ( ! control ) {
                                         break;
                                 }
+                                seen_parents[setting.menu_item_parent] = setting;
                                 setting = control.setting();
                         }
                         return depth;