Drupal 7.26 and Drupal 6.30, maintenance releases which contain fixes for security vulnerabilities, are now available for download. See the Drupal 7.26 and Drupal 6.30 release notes for further information.
Upgrading your existing Drupal 7 and 6 sites is strongly recommended. There are no new features or non-security-related bug fixes in these releases. For more information about the Drupal 7.x release series, consult the Drupal 7.0 release announcement. More information on the Drupal 6.x release series can be found in the Drupal 6.0 release announcement.
Drupal 7.26 and 6.30 were released in response to the discovery of security vulnerabilities. Details can be found in the official security advisory:
To fix the security problem, please upgrade to either Drupal 7.26 or Drupal 6.30.
(Drupal 7 only) On sites with a very large number of unpublished nodes in the database, the Taxonomy module update function introduced in this release may take a very long time to run and consume an excessive amount of memory. A fix is available in this issue and will be included in the next bug fix release of Drupal core. Sites which need the fix sooner can apply the patch from that issue to their Drupal 7.26 sites.