Trireme pillages ocean fishnet

[Tatran]

This was not possible in vanilla with galleys, maybe I missed something.
Both units can't enter ocean tiles unless there's an open border agreement.

 

[Chieftess]

There were no triremes in vanilla. You're thinking of the galley. Triremes are the warships of the ancient era, and can pillage, and you're at war with both civs - it's still inside of a culture border. So, this isn't a bug.