I had someone try to do this exact thing to me back on codemasters...and one of our friends actually gave that person their account details...you can guess what happened next..they couldnt log into their account anymore cause the password had been changed...it only took him about 2 minutes to change his password and log back on..but by that time, all his valuable items (accessories, armour, weaps, gold, stones, etc..) had been taken from his account.
just remember guys and gals...webzen will NEVER ask for your account information because they don't need to ask..if its really someone from webzen, they can just look up your account information..no need to ask for it.
so no matter what a person says to you (claim to be a gm, tell you that your account will be banned, etc...) don't listen to them and write down their name and send a ticket immediately so they can be banned.