Cross-site scripting in CKEditor5

CKSource CKEditor5 35.4.0 was discovered to contain a cross-site scripting (XSS) vulnerability via the Full Featured CKEditor5 widget.

NOTE: the vendor’s position is that this is not a vulnerability. The CKEditor 5 documentation discusses that it is the responsibility of an integrator (who is adding CKEditor 5 functionality to a website) to choose the correct security settings for their use case. Also, safe default values are established (e.g., config.htmlEmbed.showPreviews is false).