As you may know, Drupal 6 has reached End-of-Life (EOL) which means the Drupal Security Team is no longer doing Security Advisories or working on security patches for Drupal 6 core or contrib modules - but the Drupal 6 LTS vendors are and we're one of them!
Today, there is a Moderately Critical security release for the CKEditor module to fix a Cross Site Scripting (XSS) vulnerability.
The CKEditor module provides one way to integrate CKEditor into Drupal.
Due to the usage of the JavaScript eval() function on non-filtered data in the admin section, it was possible for a user with permission to create content visible in the admin area to inject specially crafted malicious script.
The problem existed in CKEditor module for Drupal, not in JavaScript libraries with the same names, however, it's highly recommended that you update to the latest version of the CKEditor JavaScript library as well, because it also recently fixed some XSS vulnerabilities.
See the security advisory for Drupal 7 for more information.
Here you can download the Drupal 6 patch or the full release.
If you have a Drupal 6 site using the CKEditor module, we recommend you update immediately! We have already deployed the patch for all of our Drupal 6 Long-Term Support clients. :-)
If you'd like all your Drupal 6 modules to receive security updates and have the fixes deployed the same day they're released, please check out our D6LTS plans.
Note: if you use the myDropWizard module (totally free!), you'll be alerted to these and any future security updates, and will be able to use drush to install them (even though they won't necessarily have a release on Drupal.org).