Barely 6 weeks after the 3.1 release – the WordPress Team are back with an update addressing some issues that have been identified.
According to the developers, the update addresses nearly 30 issues in WordPress, including three security vulnerabilities. Also they say ..
WordPress 3.1.1 corrects a cross-site request forgery (CSRF) vulnerability in the media uploader, as well as a PHP related crash caused when handling specially crafted links in comments. A cross-site scripting (XSS) issue has also been fixed.
Other changes in the release include various performance improvements, and fixes for IIS6 support, taxonomy and PATHINFO (/index.php/) permalinks, and plugin compatibility problems. All users are encouraged to upgrade to the latest release as soon as possible.
As always backup your data and database before embarking on an upgrade. I did mine in about 5 minutes but thats with a relatively small number of posts (<2000)