Today, January 19, a couple of moderately critical security updates have been released for both Drupal 7 and Drupal 9.
In short, it is an important JQuery security bug, which affects any Drupal website since Drupal uses JQuery in the frontend.
Note that there is no support for Drupal 8. If your website is a Drupal 8 then your website is insecure. All Drupal 8 and 9 versions prior to 9.2.x are end of life and do not receive security coverage.
Upgrade as soon as possible to the latest version of Drupal 9.
The links with all the official info: