only in patch2: unchanged: --- a/core/lib/Drupal/Core/Render/Element/RenderElement.php +++ b/core/lib/Drupal/Core/Render/Element/RenderElement.php @@ -269,7 +269,6 @@ public static function preRenderAjaxForm($element) { $element['#attributes']['data-disable-refocus'] = "true"; } - // Add a reasonable default event handler if none was specified. if (isset($element['#ajax']) && !isset($element['#ajax']['event'])) { switch ($element['#type']) {