Exposure of Sensitive Information to an Unauthorized Actor
The Special:Contributions page in MediaWiki before 1.22.0 allows remote attackers to determine if an IP is autoblocked via the "Change block" text.
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.