Apparently, a security flaw has been found in the Snoopy library that WordPress uses. This has made the WordPress team put out a new release, WordPress 2.6.3. According to their blog post, you only have to change that class and the file holding the version number, but an astute developer on the WordPress developer mailing list noticed that they’d slipped one other minor fix in to. So to upgrade to 2.6.3, all you have to do is download these 3 files from wordpress.org:
And overwrite them in their appropriate directories. Make very sure that you’re not overwriting the wp-includes/media.php but the one in wp-admin/includes/media.php.
Probably one of the easiest WordPress upgrades you’ve ever had in your life. It should be noted that I use the Snoopy library in several of my plugins, so you’d better upgrade!