Does anyone know what type of spider this is? (Found behind a door)
Hi there this looks like a Cheiracanthium inclusum (Agrarian Sac Spider)
This site calls the indoor ones Cheiracanthum mildei because that is an indoor species.
Yes, C. inclusum could get indoors.
They aren’t supposed to be able to be differentiated by appearance, but in my experience the outdoors ones always are a little bigger and have a greenish tan tint.