Mediawiki before 1.28.1 / 1.27.2 / 1.23.16 contains a flaw were Spam blacklist is ineffective on encoded URLs inside file inclusion syntax's link parameter.
https://security-tracker.debian.org/tracker/CVE-2017-0370
https://phabricator.wikimedia.org/T48143
https://lists.wikimedia.org/pipermail/mediawiki-announce/2017-April/000207.html