CVE 2015-6729
Cross-site scripting (XSS) vulnerability in thumb.php in MediaWiki before 1.23.10, 1.24.x before 1.24.3, and 1.25.x before 1.25.2 allows remote attackers to inject arbitrary web script or HTML via the rel404 parameter, which is not properly handled in an error page.
See the 
CVE page on Mitre.org
for more details.
