Banned member hacks ranking members account: how to get rid of login cookie?
 

One of my ranking members had their account hacked by a banned member. (hotmail brute force, followed by password retrieval) Now the forum account is compromised, as long as the banned member has the login cookie on his computer. Is there any way to reset the login status of an account or make that login cookie invalid?

Does anyone have tips how to solve this?