From 8b0a91f6027b7d74cd78541bcb0b7e7b8cd3c1ec Mon Sep 17 00:00:00 2001
From: Lauri Eskola <lauri.eskola@acquia.com>
Date: Wed, 11 Oct 2023 08:46:33 +0300
Subject: [PATCH] Issue #3351600 by andrew.farquharson, Ranjit1032002, Anybody,
 sanduhrs, gmateos, smustgrave, Wim Leers, ant1, catch:
 ckeditor5.dialog.fix.js throws "Uncaught TypeError: event.target.classList is
 undefined" in Firefox in Drupal 10 with the editor in a modal

---
 core/modules/ckeditor5/js/ckeditor5.dialog.fix.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/core/modules/ckeditor5/js/ckeditor5.dialog.fix.js b/core/modules/ckeditor5/js/ckeditor5.dialog.fix.js
index 1f4ed1d7feb..41449dcf693 100644
--- a/core/modules/ckeditor5/js/ckeditor5.dialog.fix.js
+++ b/core/modules/ckeditor5/js/ckeditor5.dialog.fix.js
@@ -12,6 +12,12 @@
     // CKEditor 5 in modals can work as expected.
     // @see https://api.jqueryui.com/dialog/#method-_allowInteraction
     _allowInteraction(event) {
+      // Fixes "Uncaught TypeError: event.target.classList is undefined"
+      // in Firefox (only).
+      // @see https://www.drupal.org/project/drupal/issues/3351600
+      if (event.target.classList === undefined) {
+        return this._super(event);
+      }
       return event.target.classList.contains('ck') || this._super(event);
     },
   });