You might have got hacked through 2 recent techniques listed on MMO Champion. The Flash player or the Google Ads vulnerabilities.

http://www.mmo-champion.com/

For the whole story check out MMO champions front page and read these 2 sections below.

Important - Adobe Flash Player Vulnerability

Quote from: Lucytr (Source)
A critical vulnerability has been discovered in Adobe Flash Player 10.0.45.2 and Adobe Reader/Acrobat 9.x, and could potentially be used to target World of Warcraft players and accounts. The newest available version of Adobe Flash 10.1, Release Candidate 7 (available at http://labs.adobe.com/technologies/flashplayer10/), does not appear to contain this vulnerability, and we recommend that everyone upgrade their Flash player as soon as possible. Earlier versions of Adobe Reader and Acrobat, specifically version 8.x, do not appear to contain this vulnerability, either.

For more information, please visit Adobe.com: http://www.adobe.com/support/security/advisories/apsa10-01.html

Get an Authenticator if you haven't got one already. Get your very own guard dog and secure your account at the same time. Visit http://us.battle.net/security for more info!

I would also like to add that this is NOT a virus. The only way to protect yourself from this kind of vulnerability is to keep your system up-to-date in all ways, including Flash.



Curse Client Google Ad Scam
A few months ago a couple of people got hacked because of malicious google ads redirecting to fake armory pages. (See this news)

The same problem is now affecting the Curse.com client that many of you use to update and download addon.