A flaw was found in moodle where logic used to count failed login attempts could result in the account lockout threshold being bypassed.
https://moodle.org/mod/forum/discuss.php?d=434582
https://bugzilla.redhat.com/show_bug.cgi?id=2083613
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-73736