Exposure of Sensitive Information to an Unauthorized Actor
api.php in MediaWiki before 1.15.5 does not prevent use of public caching headers for private data, which allows remote attackers to bypass intended access restrictions and obtain sensitive information by retrieving documents from an HTTP proxy cache that has been used by a victim.
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.