Yes, if it has nothing on it but the poison symbol, the attack is unchanged. It's +0 poison.

On character sheet of the demolitionist there is a  perk "replace one -1 card with one +0 posion card.

However, i do not have a +0 posion card. I do have a posion card (without the +0)
Does this card counts as +0 attack and add poision? Or is this a null attack and posion?

This because there also are other cards in the deck with "+0" on it, but on the posion card this number isnt shown

Demolitionist perk question