We're encountering a new major problem on the French Wiktionary for a few hours: https://fr.wiktionary.org/w/index.php?title=Wiktionnaire:Wikidémie#Ajout.C3.A9_.C3.A0_la_cat.C3.A9gorie
The recent changes and the watchlists are displaying the pages categories instead of the pages titles, for the most part of the entries!
This occurred with different users from different places, at least under Monobook and Vector, Firefox and Edge, also with no gadget, and MediaWiki:Common.js hasn't been touched.