Maintenance and security release of the Drupal 6 series.
This release fixes security vulnerabilities. Sites are urged to upgrade immediately after reading the security announcement:
No other fixes are included.
No changes have been made to the .htaccess, robots.txt or default settings.php files in this release, so upgrading custom versions of those files is not necessary.
See below for small API changes that may affect sites which use alternative page cache implementations and that expose Ajax or multi-step forms to anonymous users on cached pages.
In most cases, serious regressions are not expected and the changes are not critical.
Major changes since 6.30:
Modules which provide alternative page cache implementations require updates for Drupal 6.31 and Drupal 7.27
This is expected to affect modules such as Boost or other modules which provide alternative page cache implementations that write pages to to the cache under different conditions than Drupal core normally does.