yeah, I'd STRONGLY recommend that you send a GM a private message right away explaining how you exploited the bug.. I don't know if they have already figured it out exactly or not, but I do know that they generally appreciate when players help them find and fix bugs
... just don't post it publicly - don't want to show others how to abuse it while it's being fixed
Not only is it good for you to report how you abused this bug, so that the GM team will go easy on you - but providing this information could very well get you a nice reward. There are many bugs that pop up over time, and it is not easy to fix these things - especially when we are not aware of them or not aware of how they are caused. That is why we reward players for bringing this information to us.