Give me a link to the exact page you are on when this pops up. The chances of you getting a malicious ad twice on the exact same page is infinitesimally small. That doesn't mean there isn't an issue somewhere on the page.
I had something similar several years ago, it was changing random words in posts into clickable links to product pages. Virus scans didn't detect anything, I eventually found it as a browser add on, once uninstalled the issue was gone.
This is a tough one... but especially considering you got hit with the same thing twice, chances are high that it is something on your end. I am doing a deep dive on this end and would encourage you to do the same.
I've run AVG twice and it hasn't come up with anything. I had a virus redirector warning on eBay and I Googled it and numerous people have had that and said it's in ads running on ebay. I wonder if something like that is happening here?