Drupal 6.11 and 5.17, maintenance releases fixing problems reported using the bug tracking system, as well as a critical security vulnerability, are now available for download. Drupal 6.11 also fixes performance issues with the menu cache and update status cache among other smaller issues.
Upgrading your existing Drupal 5 and 6 sites is strongly recommended.
For more info see Drupal 6.11 and 5.17 released, SA-CORE-2009-005 - Drupal core - Cross site scripting and Upgrade Drupal to 6.11.
To view upgrade pricing, comments and other info you need an account. To request one contact me.