The wiki subsystem in Moodle through 2.3.11, 2.4.x before 2.4.9, 2.5.x before 2.5.5, and 2.6.x before 2.6.2 does not properly restrict (1) view and (2) edit access, which allows remote authenticated users to perform wiki operations by leveraging the student role and using the Recent Activity block to reach the individual wiki of an arbitrary student.