Ticket #33312: 33312.patch

src/wp-includes/js/wp-a11y.js

@@ -41 +41 @@
                 ariaLive = ariaLive || 'polite';
                 role = 'assertive' === ariaLive ? 'alert' : 'status';
 
+                if ( null !== window.frameElement ) {
+                        return;
+                }
+
                 var $container = $( '<div>', {
                         'id': 'wp-a11y-speak-' + ariaLive,
                         'role': role,