Permissions, Privileges, and Access Controls
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.
CWE-264 - Permissions Privileges and Access Controls
CWE 264 (permissions, privileges, and access controls) is not a weakness in and of itself, rather it is a category of weaknesses related to the management of permissions, privileges, and other security features used to perform access control. If not addressed, the weaknesses in this category allow attackers to gain privileges for an unintended sphere of control, access sensitive information, and execute arbitrary commands.