Awkward situation... I might accidently out myself or worse!

I am concerned about a recent conversation I had with a group of friends. They actually started a bet on whether I watch porn or not. Of course, they have no way to verify whether I watch porn or not (They themselves stated that) but I don't know how to handle the conversation. If I say the wrong thing to them about this topic I could potentially out myself. I would simply forget that this happened, but they will surely bring it up tomorrow.