Drupal 7.18 and 6.27 maintenance releases which contain fixes for security vulnerabilities are now available.
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.
Drupal 7.18 and 6.27 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 7.18 or Drupal 6.27.