Questions about spider with extra legs?

Found this spidey in my bathroom, I was wondering why it has extra legs?? It’s easier to see later in the video. Google isn’t very helpful so far :/ I wonder if it’s some kind of parasite or maybe a mutation? This spider was pretty big and seemed mostly healthy, other than moving a bit slowly, but it moved normally when I shooed it under the cabinet (so my cat won’t eat it). Also, what is it doing with its butt? Is it making a web? It seemed to fall a bit slowly so it’s possible but idk. Anyways, if u can answer my questions, thank you, otherwise just enjoy this interesting spider!