The MoodleQuickForm class in lib/formslib.php in Moodle through 2.1.10, 2.2.x before 2.2.10, 2.3.x before 2.3.7, and 2.4.x before 2.4.4 does not properly handle a certain array-element syntax, which allows remote attackers to bypass intended form-data filtering via a crafted request.
https://moodle.org/mod/forum/discuss.php?d=228935
http://openwall.com/lists/oss-security/2013/05/21/1
http://lists.fedoraproject.org/pipermail/package-announce/2013-May/107026.html
http://lists.fedoraproject.org/pipermail/package-announce/2013-May/106988.html
http://lists.fedoraproject.org/pipermail/package-announce/2013-May/106965.html
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-38885