Moodle 1.9.x before 1.9.18, 2.0.x before 2.0.9, 2.1.x before 2.1.6, and 2.2.x before 2.2.3 allows remote authenticated users to bypass the moodle/calendar:manageownentries capability requirement and add a calendar entry via a New Entry action.
https://moodle.org/mod/forum/discuss.php?d=203057
http://www.securityfocus.com/bid/53626
http://openwall.com/lists/oss-security/2012/05/23/2
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-18335