Exposure of Sensitive Information to an Unauthorized Actor
mod/forum/user.php in Moodle 1.9.x before 1.9.16 allows remote authenticated users to obtain the names and other details of arbitrary user accounts by searching for posts.
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.