Content complements of: https://wordpress.org/news/2015/07/wordpress-4-2-3/
WordPress 4.2.3 is now available. This is a security release for all previous versions and we strongly encourage you to update your sites immediately.
WordPress versions 4.2.2 and earlier are affected by a cross-site scripting vulnerability, which could allow users with the Contributor or Author role to compromise a site. This was initially reported by Jon Cave and fixed by Robert Chapin, both of the WordPress security team, and later reported by Jouko Pynnönen.
We also fixed an issue where it was possible for a user with Subscriber permissions to create a draft through Quick Draft. Reported by Netanel Rubin from Check Point Software Technologies.
Our thanks to those who have practiced responsible disclosure of security issues.
WordPress 4.2.3 also contains fixes for 20 bugs from 4.2. For more information, see the release notes or consult the list of changes.
Download WordPress 4.2.3 or venture over to Dashboard → Updates and simply click “Update Now.” Sites that support automatic background updates are already beginning to update to WordPress 4.2.3.
Thanks to everyone who contributed to 4.2.3:
Aaron Jorbin, Andrew Nacin, Andrew Ozz, Boone Gorges, Chris Christoff, Dion Hulse, Dominik Schilling, Ella Iseulde Van Dorpe, Gabriel Pérez, Gary Pendergast, Mike Adams, Robert Chapin, Nikolay Bachiyski, Ross Wintle, and Scott Taylor.