Moodle 2.9.x before 2.9.3 does not properly check the contact list before authorizing message transmission, which allows remote authenticated users to bypass intended access restrictions and conduct spam attacks via the messaging API.Referenceshttp://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-50426https://moodle.org/mod/forum/discuss.php?d=323228
