CVE 2016-2154

admin/tool/monitor/lib.php in Event Monitor in Moodle 2.8.x before 2.8.11, 2.9.x before 2.9.5, and 3.0.x before 3.0.3 does not consider the moodle/course:viewhiddencourses capability, which allows remote authenticated users to discover hidden course names by subscribing to a rule.

See the CVE page on Mitre.org for more details.