WordPress 4.2.2 is now available.
This is a critical security release for all previous versions and we strongly encourage you to update your sites immediately.

Version 4.2.2 addresses two security issues:

The Genericons icon font package, which is used in a number of popular themes and plugins, contained an HTML file vulnerable to a cross-site scripting attack. All affected themes and plugins hosted on WordPress.org (including the Twenty Fifteen default theme) have been updated today by the WordPress security team to address this issue by removing this nonessential file. To help protect other Genericons usage, WordPress 4.2.2 proactively scans the wp-content directory for this HTML file and removes it. Reported by Robert Abela of Netsparker.
WordPress versions 4.2 and earlier are affected by a critical cross-site scripting vulnerability, which could enable anonymous users to compromise a site. WordPress 4.2.2 includes a comprehensive fix for this issue. Reported separately by Rice Adu and Tong Shi.
0-days in the wild

What is interesting about this attack is that we detected it in the wild days before disclosure. We got a report about it and some of our clients were also getting reports saying they were vulnerable and pointing to:

http:// site.com/wp-content/themes/twentyfifteen/genericons/example.html#1<img/ src=1 onerror= alert(1)>

In this proof of concept, the XSS printed a javascript alert, but could be used to execute javascript in your browser and take over the site if you are logged in as admin.
WordPress 4.2.2 also contains fixes for 13 bugs from 4.2. For more information, see the release notes or consult the list of changes.


For more information: https://wordpress.org/news/2015/05/wordpress-4-2-2/