CKEditor 4.x before 4.11.0 allows user-assisted XSS involving a source-mode paste.
https://www.oracle.com/technetwork/security-advisory/cpujul2019-5072835.html
https://ckeditor.com/cke4/release/CKEditor-4.11.0
https://ckeditor.com/blog/CKEditor-4.11-with-emoji-dropdown-and-auto-link-on-typing-released/