Two new releases of the extremely popular open source content management system, Drupal, are available for public consumption. These new versions cover both the 5.x series and the 6.x series.
You can preview the Drupal 6.15 release notes as well as the Drupal 5.21 release notes to see the full list of changes.
Drupal recommends that you do a full upgrade (which is also detailed in the security announcement) as the patches do not contain the additional bug fixes that went into the releases. Applying the patches will leave your site in an unversioned state and confuse the update status module, which will keep reminding you to upgrade to 6.15 or 5.21. Please read the announcement for details on the patch.