This night (in my timezone), two users reported that the ManageWiki menu disappeared from the sidebar and this apparently also happened to all of my wikis as well (and I haven't made any modifications recently)
One user in specific reported they can no longer edit user groups, all of a sudden.
On my account specifically there's no problem with permissions, I still can access by typing the URL, but not sure about other users.

Examples:
http://marionetwork.miraheze.org/ (my wiki)
https://ranchstory.miraheze.org/wiki/