Description
An issue was discovered in MediaWiki before 1.37.3 and 1.38.x before 1.38.1. The contributions-title, used on Special:Contributions, is used as page title without escaping. Hence, in a non-default configuration where a username contains HTML entities, it won't be escaped.
Remediation
References
Related Vulnerabilities
WordPress Plugin GNU-Mailman Integration Cross-Site Scripting (1.0.6)
MediaWiki Exposure of Sensitive Information to an Unauthorized Actor Vulnerability (CVE-2013-4569)
WordPress 'wp-register.php' Multiple Cross-Site Scripting Vulnerabilities (2.0 - 2.0.1)
WordPress Plugin Slideshow Gallery 2 'border' Parameter Cross-Site Scripting (1.1.4)