Check this query: https://wiki.archlinux.org/api.php?action=query&prop=categories&titles=ArchWiki:About&clshow=!hidden
{ "batchcomplete": "", "query": { "pages": { "943": { "pageid": 943, "ns": 4, "title": "ArchWiki:About", "categories": [ { "ns": 14, "title": "Category:ArchWiki" }, { "ns": 14, "title": "Category:Pages where expansion depth is exceeded" } ] } } } }
The API returned Category:Pages where expansion depth is exceeded even though clshow=!hidden is given in the query string.
What is also weird about this category is that its page indicates there are many category members, but when visiting any of the pages, it is not listed among the categories of the page (not even among the hidden categories when the user logs in). Is the category hidden even from the hidden categories?
None of this was happening with MediaWiki 1.36.