There's a Firefox extension called Priv8 [1] which is meant to do that.
However, given that FF doesn't have sandboxes and SOP is (AFAIK) the main isolation system, I wonder whether it's possible for one origin to somehow sniff the presence of different sessions in the same client via, say, some JS info leak.
However, given that FF doesn't have sandboxes and SOP is (AFAIK) the main isolation system, I wonder whether it's possible for one origin to somehow sniff the presence of different sessions in the same client via, say, some JS info leak.
[1] http://143th.net/post/105342885096/priv8-is-out