Yeah, but this only started a few days back, while I've been visiting this site for a couple years now.
And so ? Haven't you noticed that you don't see the same ad every time you refresh the forum, and that the ads you see today are not the ones you used to see last year ?
Advertisement services are near to, if not the, first method used nowadays to spread malwares and viruses. It doesn't matter if only one hour pass before they are removed by the said service, due to the malicious behavior, the time the ad was in the advertisement pool is generally enough to caught some preys.
Like I said, congratulation, your antivirus is doing is job.
The only thing that happened relevant to this topic on my end is [...]
And as I said, the problem do not come from your end. I answered your question, and the answer I gave you is the exact reason why your antivirus warn you, with reason, about a suspicious behavior.