It was just announced that WordPress 2.6.3 has been released due to a security issue in something called Snoopy. Snoopy is something that grabs the feeds that are displayed in your dashboard. It’s supposed to be a relatively minor risk. If you don’t want to download the whole upgrade, you can get the following 2 files from the release post:

• wp-includes/class-snoopy.php
• wp-includes/version.php

And replace them. I just upgraded and it was a pretty painless process.