I really don't believe the problem is malicious ads at this point, but rather something wrong with the way the ads are being rendered on the site itself. When I was testing the trending threads directory issue with/without ad blocker and with/without being logged in, there was a huge difference in the way the site rendered while logged in with ad blockers off. Chrome being the browser with the worst issues, I was never able to fully render a single FT page using Chrome with no ad blocker while being logged in, the loading icon just spun for eternity.

My guess is that at least one of the ads from the current ad network has a compatibility issue with the site and Chrome is trying to render it endlessly, causing a huge CPU spike, even though the actual content of the page fully loads and renders. Unfortunately, I have no idea how to possibly isolate a problematic ad or a potential coding compatibility issue from the user side so I don't think I'll be able to help there like I could isolating the trending threads directory problem.