WordPress 3.1.1 is now available. This maintenance and security release fixes almost thirty issues in 3.1, including:
Version 3.1.1 also addresses three security issues discovered by WordPress core developers Jon Cave and Peter Westwood, of our security team. The first hardens CSRF prevention in the media uploader. The second avoids a PHP crash in certain environments when handling devilishly devised links in comments, and the third addresses an XSS flaw.
You can update from your Dashboard or download from http://www.wordpress.org