Among Microsoft's updates are fixes for a trio of zero-day vulnerabilities. This includes an expected patch for a flaw in the Windows domain name system, or DNS. The vulnerability affects Windows 2000 Server and Windows Server 2003. Microsoft warned of the problem last month and has said it was being used in "limited" attacks.
If you are using automatic updates, you should already have the patches downloaded. If not, it's a good to go snag them.