report/outline/index.php in Moodle 2.2.x before 2.2.7, 2.3.x before 2.3.4, and 2.4.x before 2.4.1 does not properly enforce the moodle/user:viewhiddendetails capability requirement, which allows remote authenticated users to discover a hidden lastaccess value by reading an activity report.
Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.