Exposure of Sensitive Information to an Unauthorized Actor
Redmine before 4.1.5 and 4.2.x before 4.2.3 may disclose the names of users on activity views due to an insufficient access filter.
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.