Versions of WordPress 3.0 up to 3.9.2 were discovered to contain a security vulnerability through the comment features on the site, making a large number of installs and servers vulnerable to attack. The bug was discovered by Jouko Pynnonen of the Finnish IT company Klikki Oy, indicating that the bug went unchecked for more than four years since it was introduced with version 3.0 in June 2010.
