I've just upgraded to Yosemite and hit up against the bug mentioned already here.
Following the thread I couldn't see any definitive instruction as to how to fix it.
Hence I have just downloaded and installed 1.23.5, which does work, although you need to reboot your machine first, otherwise it complains that something (namely 1.23.3) is using the default 8080 port.
Now I'm trying to copy my wiki across into the new version. I've tried deleting /Applications/mediawiki-1.23.5-0/apps/mediawiki/htdocs/* and copying the 1.23.3 htdocs/* over, but this doesn't work. It doesn't change the homepage.
What is the proper way to do this?