WordPress 2.3.3 has been released and is an urgent security release. At the very minimum you need to update your xmlrpc.php file.

WordPress MU 1.3.3 has been released as well due to the same security fix.

Also of note, there is a vulnerability in the WP-Forum plugin that is being actively exploited right now. If you are using this plugin, please remove it until an update is available.

If you need assistance with upgrading, please contact us.