It drowned. You can repair it, and then give it a conformal coat to protect it from further damage, but you should also fix where it is getting water in. My bets are fia the window edge and through the door latch, along with it coming through inside when you drip on the door itself. Place some sheet plastic to cover the board from the top and sides, leaving the bottom open to allow drainage and the new one will last longer.
the black is corrosion of inside tracks and layers, and the white is from areas which are always 12V supplies that got wet.