Wikimedia has recently switched to HTTPS [1]; due to some unexpected
problems
this caused for third-party wikis, the domains used by the InstantCommons
[2]
feature continued to support HTTP. That ends now; in a few day, these
connections
will be redirected to HTTPS.
MediaWiki was updated to correctly deal with this in 1.25.2, 1.24.3, and
1.23.10 [3]; if you use InstantCommons with an older version of MediaWiki,
you
should upgrade. The latest version (1.25.3, 1.24.4 and 1.23.11 [4]) includes
some improvements to MediaWiki's HTTPS support on platforms where cURL is
not
available; if you are encountering problems, make sure you use this version.
If you absolutely cannot upgrade, you can find workarounds in T102566 [5].
[1]
http://blog.wikimedia.org/2015/06/12/securing-wikimedia-sites-with-https/
[2]
https://www.mediawiki.org/wiki/InstantCommons
[3]
https://lists.wikimedia.org/pipermail/mediawiki-announce/2015-August/000179…
[4]
https://lists.wikimedia.org/pipermail/mediawiki-announce/2015-October/00018…
[5]
https://phabricator.wikimedia.org/T102566