Well this is yet another really old bug that was never fixed. I posted a bug report in game ages ago. I also found someone had posted (essentially the same thing) in this forum about a year ago which was left unanswered and untouched. I tried to make a post in that thread to say the bug was still around - woops. Didn't realise the thread was out of date, and got a forum warning for my trouble... But if the thread was out of date, why did it allow me to add a new post? Sigh - not even STO forums are free of bugs - same old story with cryptic. But anyway, off topic......
There are weapons in game that are showing the incorrect MK stats information. For example, most noticeably so far I have found is the QUANTUM TORPEDO LAUNCHER MK-12 (of any type and any rareity I think).
***OK to make things simple to understand here, lets say you've found a COMMON quantum torp (rather than confuse with all the other rarer versions with all their damage "bonuses" etc). So it's just a plain common MK-12 quantum torp that you have found (I'm pretty sure commons are affected too).***
If you look at its PICTURE in your inventory, then it shows it to be a MK-12. However, hover over the item with your cursor, and the stats information says this item to be a Mk-11. Also if you ctrl+left-click on the item the MK stats still thinks this item is MK-11 Interestingly though, if you compare one of these bugged MK-12's commons to a "real" MK-11 common (as far as I know MK-11's show the correct MK rank in picture and all stats info), the DPS / DMG information for the MK-12 version IS higher than the MK-11. So presumably these buggy MK-12's do do their correct DPS / DMG in battle, but they just show the incorrect MK rank.
(But on the other hand their DMG might be wrong too - if little details like the wrong MK rank are wrong, how can we be sure any of the DMG and other stuff works the way it's really supposed to? This is something else that needs to be looked into).
Anyway as this MK-12 item seems to think it's a MK-11 item, this is also mesing up searching for it in the exchange. You must type in "Quantum Torpedo Launcher Mk XI" in the search box to find the MK-12's on the list. With the 2 MK's mixed up, it makes things hard to figure out and find.
Trouble is, as I said above, years ago I made the same kind of bug report as this - concerning another weapon or weapons (that I cannot remember now) which was also showing incorrect MK or Stats. So I have no idea if that was ever fixed, or just how many more weapons in game have this problem.
I think this problem is mostly isolated to weapons - I have not found any problems with any other things like consoles etc (but doesn't mean to say they aren't there).