Please do not go posting thread titles in capital letters and shouting "exploit", it causes unnecessary worry/concern.
Firstly, this has been reported before by numerous users and has been known by more, for want of a better word, "experienced" mIRC users for a number of months now. Khaled is aware of the issue. The seriousness of the issue is up for debate of course, both arguments resting quite a bit on presumptions which we don't need to go over in this thread, or any other.
At this time, the BUG is not anywhere near widespread enough to be considered particularly dangerous. It is however a
potential serious threat if used properly in the right circumstances. Neither this thread or any other will be used to post methods of exploitation. Attempts at doing so will get threads deleted. Plenty of info and discussion has been sent to Khaled and Krejt too.
I would give two points of advice. One, if you have Autojoin On Invite enabled, you can turn it off with
/ajinvite off. If you're not an avid user of this feature but have it turned on for no particular reason, it would be wiser to turn it off. If you use the feature a lot then feel free to continue using it without worry. Secondly, a point which has been raised countless times in the past - please remember not to type anything people tell you to type unless you know for certain what the outcome of it will be.
Thanks for your concern Dean, but don't get too dramatic just yet

Regards,