Am I going insane right now?

There's a 4-legged spider climbing up my bathroom wall right now. 4 large spindly legs. I'm pretty sure there's no such thing as a 4-legged spider, as far as I know all species have 8 legs. Is it possible this one was born with a congenital defect? I doubt that it lost the other 4 legs in an accident as the legs that it currently have are evenly spaced and it doesn't look injured. It's walking away fine with the 4 legs.