It is unlikely that it has anything to do with the addon directly, Alamir, unless you installed it with an executable program. You may have picked up a keylogger or other malicious software around the time that you got it though.

Please review the following.

http://us.battle.net/en/security/commitment

Once you have checked your system it would probably be a good idea change your password and the password on your registered e-mail address.

Once you log back in check your characters. If you are missing any items/gold, please submit a petition and let us know.