I can’t replicate it either. The site in question is fairly busy and I’ve only seen it happen that once.
Thank you both for the insight into how this may have happened. It sounds like someone’s browser requested an image from another website for some reason and wordpress/super-cache created the directory structure to match that failed request. That’s a relief, I was panicking when I first saw it.
My webhost (dreamhost) has the directory structure set up a little differently than most hosts. My / dir contains folders with the names of the domains in my account, and each of those is it’s own “root” for that site. Those folders themselves are chmodded 755.
I’m using the sandbox template, which I believe does something differently with 404 pages, beyond that is beyond me.
