Enhanced Steam

Website's up for me.
I accepted the permissions already, and it was fine but I just got randomly logged out of steam. And since your post made me paranoid, I disabled ES before logging in, and it rejected my password like 3 times which scared me further, but then accepted it because apparently I just can't type for shit.

So to answer your question: no idea

Asking for permissions is normal, depending on what the extension needs to do. The only strange thing about it was that it was asking for permission for sites I would have imagined it already asked for on install.