Exposure of Sensitive Information to an Unauthorized Actor
user/index.php in Moodle through 2.6.11, 2.7.x before 2.7.13, 2.8.x before 2.8.11, 2.9.x before 2.9.5, and 3.0.x before 3.0.3 grants excessive authorization on the basis of the moodle/course:viewhiddenuserfields capability, which allows remote authenticated users to discover student e-mail addresses by leveraging the teacher role and reading a Participants list.
CWE-200 - Information Exposure
An information exposure vulnerability is categorized as an information flow (IF) weakness, which can potentially allow unauthorized access to otherwise classified information in the application, such as confidential personal information (demographics, financials, health records, etc.), business secrets, and the application's internal environment.