The announcement message for 1.23.13 includes a patch link to the 1.23.12 version:
https://lists.wikimedia.org/pipermail/mediawiki-announce/2015-December/000187.html
The announcement message for 1.23.13 includes a patch link to the 1.23.12 version:
https://lists.wikimedia.org/pipermail/mediawiki-announce/2015-December/000187.html