Exposure of Sensitive Information to an Unauthorized Actor
MediaWiki through 1.23.15, and 1.24.0-rc.0 though 1.27.1 allows remote attackers to discover the IP addresses of Wiki visitors via a style="background-image: attr(title url);" attack within a DIV element that has an attacker-controlled URL in the title attribute.
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.