MY VEHICLE WAS IN PARK ON MY STREET. MY HUSBAND WAS IN THE PASSENGER SEAT. I EXITED THE DRIVER SIDE OF THE VEHICLE AND OPENED THE DRIVER SIDE REAR DOOR. I KNEELED ON THE SEAT TO REACH BEHIND THE PASSENGER SIDE SEAT TO GRAB MY LAUNDRY BASKET. THE CAR BEGAN TO ROLL BACKWARDS. WE HIT A VEHICLE DIRECTLY BEHIND US AND ENDED UP IN OUR NEIGHBORS YARD. WE CONTACTED THE POLICE AND A TOW TRUCK WAS SENT. THE TOW TRUCK ARRIVED FROM JOYCE'S TOWING ON MT. NEBO ROAD IN PITTSBURGH PA. THE TOW TRUCK DRIVER NOTICED THAT WHILE THE CAR WAS IN PARK THE WHEELS WERE SPINNING. THE BODY SHOP IN WHICH WE TOOK OUR VEHICLE TO, IS HAVING AN ISSUE TRYING TO DUPLICATE THE PROBLEM. IN THE MEANTIME, I DO NOT FEEL THAT OUR VEHICLE IS SAFE, AND DO NOT WANT TO RISK THIS INCIDENT HAPPENING AGAIN, BEING THAT IT WAS AN ISSUE IN 2011-2014 HYUNDAI SONATAS.