lib/db/upgrade.php in Moodle 2.0.x before 2.0.5 and 2.1.x before 2.1.2 does not set the correct registration_hubs.secret value during installation, which allows remote attackers to bypass intended access restrictions by leveraging the hubs feature.
https://bugzilla.redhat.com/show_bug.cgi?id=747444
http://moodle.org/mod/forum/discuss.php?d=188315
http://git.moodle.org/gw?p=moodle.git%3Ba=commit%3Bh=ca896fdfcfcc87846fa91a297d0aa6999a68c48a