whatsapp owns the systems, so its up to whatsapp to sue
You can’t sue a dude for stealing a screwdriver to break into your home with. Your tort is the act against you.
So if someone robs a bank and empties my safety deposit box I can't sue them because it was the bank that had the money, not me?
(One might argue that it's similar with "your" money ((in the bank)) , but that's not the point)
You can sue the thief for stealing your property and the bank for negligent bailment. Same concept as a valet crashing your car.
You can’t sue a dude for stealing a screwdriver to break into your home with. Your tort is the act against you.