It has been reported in the news that there is a security vulnerability with a script called timthumb.php, which is commonly used for uploading and sizing images in PHP applications, especially WordPress.

If you’re using timthumb.php on your website, you need to replace it with a new and more secure version. The latest secure version can be obtained directly form the developers of timthumb.php at:
http://timthumb.googlecode.com/svn/trunk/timthumb.php

More information about the timthumb.php script can be found at the developer’s homepage:
http://www.binarymoon.co.uk/projects/timthumb