Is it from this? I got that long ago, but I got rid of it using that method.
This problem with ads is strange because here I've never seen any ads in the forum since I became member. The forum is free of ads and I don't use ad blockers.
Do a scan with your antivirus, see your browser extensions and so on. For my experience with the forum, the problem is not with it.
And I access this forum at least in 3 different computers, in 2 different browsers (Chrome and Firefox), no adblockers in anyone, and I get the same problem in all of them. So I'm pretty sure it's not a problem of my hardware/OS/browser.