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.