/etc/mediawiki-extensions/extensions-available/Renameuser.php is in mediawiki 1:1.27.4-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/mediawiki/extensions-core/Renameuser/Renameuser.php
/usr/share/mediawiki/extensions-core/Renameuser/Renameuser.php