Mediawiki v1.40.0 does not validate namespaces used in XML files.
Therefore, if the instance administrator allows XML file uploads,
a remote attacker with a low-privileged user account can use this
exploit to become an administrator by sending a malicious link to
the instance administrator.
An issue was discovered in MediaWiki before 1.35.11, 1.36.x through 1.38.x before 1.38.7, 1.39.x before 1.39.4, and 1.40.x before 1.40.1. It is possible to bypass the Bad image list (aka badFile) by using the thumb parameter (aka Manualthumb) of the File syntax.