Moodle 2.0.x before 2.0.9, 2.1.x before 2.1.6, and 2.2.x before 2.2.3 allows remote authenticated users to bypass an activity's read-only state and modify the database by leveraging the student role and editing database activity entries that already exist.
Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.