Risa

Yeah that's trending towards the grey goo scenario, isn't it?

But it's also similar to how the Borg operate too. Also I think the OST had the Doomsday Machine episode that had something about a weapon killing the civilization that made it. I think there was a TNG episode like that too.

So it's kinda covered, just not exactly the replicator scenario. But that's fine, it's better to have characters as a threat rather than machines. Controversial opinion, but I even found the Borg to be boring after Best of Both Worlds.

Of course, there’s always the threat of them going rogue or being taken over by someone else.

In lower decks they explored this a little with the Texas class automated ships. They weren't self-replicating but they showcased the risks of such a technology.