MediaWiki through 1.32.1 has Incorrect Access Control (issue 1 of 3). A spammer can use Special:ChangeEmail to send out spam with no rate limiting or ability to block them. Fixed in 1.32.2, 1.31.2, 1.30.2 and 1.27.6.
https://www.debian.org/security/2019/dsa-4460
https://seclists.org/bugtraq/2019/Jun/12
https://phabricator.wikimedia.org/T209794
https://lists.wikimedia.org/pipermail/wikitech-l/2019-June/092152.html