Can was opened, it was still in the can. Cooked with it at 5pm and found it at 1am when I was feeding my daughter.
I would be inclined to say it's fine. Not as if it is raw seafood!
Tomato paste is fairly acidic, so for that amount of time I would feel comfortable keeping it. However, I would use it quickly or put the rest of it in the freezer in another container. The paste can mold eventually, even refrigerated.
It's in my freezer now! Thanks :)