The Special:DeletedContributions page in MediaWiki before 1.23.10, 1.24.x before 1.24.3, and 1.25.x before 1.25.2 allows remote attackers to determine if an IP is autoblocked via the "Change block" text.
https://phabricator.wikimedia.org/T106893
https://lists.wikimedia.org/pipermail/mediawiki-announce/2015-August/000179.html
https://github.com/wikimedia/mediawiki/commit/5faabfa1bbf65536ea36108887040198afcb3c82
http://www.openwall.com/lists/oss-security/2015/08/27/6
http://www.openwall.com/lists/oss-security/2015/08/12/6
http://lists.fedoraproject.org/pipermail/package-announce/2015-August/165193.html