A cross-site scripting (XSS) vulnerability in the HTML Data Processor in CKEditor 4 4.14.0 through 4.16.x before 4.16.1 allows remote attackers to inject executable JavaScript code through a crafted comment because --!> is mishandled.
https://www.drupal.org/sa-core-2021-003
https://lists.debian.org/debian-lts-announce/2021/11/msg00007.html