Drupal 6.13 and 5.19, maintenance releases fixing problems reported using the bug tracking system, as well as critical security vulnerabilities, are now available for download. Both releases fix some other smaller issues as well.

Upgrading your existing Drupal 5 and 6 sites is strongly recommended. There are no new features in these releases. For more information about the Drupal 6.x release series, consult the Drupal 6.0 release announcement, more information on the 5.x releases can be found in Drupal 5.0 release announcement.

The full list of changes between the 6.12 and 6.13 releases can be found by reading the 6.13 release notes. A complete list of all bug fixes in the stable DRUPAL-6 branch can be found at http://drupal.org/project/cvs/3060/?branch=DRUPAL-6.

The full list of changes between the 5.18 and 5.19 releases can be found by reading the 5.19 release notes. A complete list of all bug fixes in the stable DRUPAL-5 branch can be found at http://drupal.org/project/cvs/3060/?branch=DRUPAL-5.
Security vulnerabilities

Drupal 5.19 and 6.13 were released in response to the discovery of security vulnerabilities. Details can be found in the official security advisory:

    * SA-CORE-2009-007

To fix the security problem, you can either (1) upgrade Drupal or (2) patch Drupal.

We strongly recommend you do the 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 6.13 or 5.19. Please read the announcement for details on the patch.

If you still prefer to patch Drupal, apply the http://drupal.org/files/sa-core-2009-007/SA-CORE-2009-007-6.12.patch file to your Drupal 6.12 codebase or http://drupal.org/files/sa-core-2009-007/SA-CORE-2009-007-5.18.patch to your Drupal 5.18 codebase.
Important update notes

It is important to run update.php. These releases did not change the .htaccess, robots.txt and (default.)settings.php files, so you can keep your existing files intact, if you have modifications in them