Mediawiki before 1.28.1 / 1.27.2 / 1.23.16 contains an information disclosure flaw, where the api.log might contain passwords in plaintext.
https://security-tracker.debian.org/tracker/CVE-2017-0361
https://phabricator.wikimedia.org/T125177
https://lists.wikimedia.org/pipermail/mediawiki-announce/2017-April/000207.html