i found a quest using some of this items: https://classic.wowhead.com/quest=9121/the-dread-citadel-naxxramas

quest filter off:

a few items examples:

If you activate the following filter this should be fixed.

@Chanizu already all checked in my account less black market items to track mounts and pets from BMAH

Hm.. strange, i'll take a peek at it a bit later :)

I don't understand, what's the issue here?

this items are showing in default a source removed from game, happen in the past with other item #65 and naxx 40 stuff showing up in shadowlands att is strange too

/att item:12363 in-game doesn't show the old Naxx 40 source. In fact, even in Debug it shows no sources, so it's likely not listed anywhere specifically in the DB anymore. Either logic changed to fix this or source data changed. Going to mark this as Closed and we can have a new issue if another specific example is found.