Version 2.5.1 of WordPress is now available. It includes a number of bug fixes, performance enhancements, and one very important security fix. We recommend everyone update immediately, particularly if your blog has open registration. The vulnerability is not public but it will be shortly.

The notice also mentioned the SECRET_KEY thing that I talked about yesterday and gave a link to auto-generate the line for wp-config.php:

Since 2.5 your wp-config.php file allows a new constant called SECRET_KEY which basically is meant to introduce a little permanent randomness into the cryptographic functions used for cookies in WordPress. You can visit this link we set up to get a unique secret key for your config file. (It’s unique and random on every page load.) Having this line in your config file helps secure your blog.

Upgrading took me about 15 seconds (as usual), mostly to find the svn command in the codex again and then a few seconds to run it and a few seconds in hitting the “database upgrade” page on the site before things were all done.