Mine was. This includes all their sites; Lifehacker, io9, and more.
If your account was hacked and you use that password elsewhere, you need to change it at all other sites that use it.
Slate has the super-useful form. Put in your email or username and it’ll tell you if it was hacked.
Nope
Well, I was. This means I have to change my password for all my sites from “password” to something else, doesn’t it? 🙂