vBulletin Malware Popups & Popunders?
 

I apologize if I'm posting on the wrong board but since it does say "software"... I'm on vBulletin 3.7.4 and twice already I've had somebody or something "inject" malicious code on my template causing my site to have malware pop-ups & pop-unders. What causes this? Is there a problem with my...