lib/modinfolib.php in Moodle 2.0.x before 2.0.10, 2.1.x before 2.1.7, 2.2.x before 2.2.4, and 2.3.x before 2.3.1 does not check for a group-membership requirement when determining whether an activity is unavailable or hidden, which allows remote authenticated users to bypass intended access restrictions by selecting an activity that is configured for a group of other users.