GDNet site is getting really scary now, while reading
Keep in mind this isn't just GameDev it's affecting. I've personally seen the exact same redirect on several large, high-profile sites - although not here yet. These ads are making it through the Adsense filters and for some reason are very difficult to find.
While knowing the thread is helpful if it's a malicious user, in this case it is an ad from Adsense. What we need is the banner or url that is causing the redirect before the pop-up happens.