Is my friend liable for my medical bills if was bitten by their dog?

I was invited to my friend’s house. When I arrived at their house, nobody answered the front door. I heard my friend’s voice in the backyard. I unlocked gate and entered the backyard. I called out to my friend letting them know I had arrived when there pit-bull attacked me. I was unaware that the said friend had this dog. I also later found out that this dog has previously bitten another person. I also have found out that the dog has never been vaccinated.