Last week, myself and several others were getting Avast URL:Mal alerts when playing YouTube videos. I got help from here and ran the malware tools. I was told everything looked clean. I then noticed that someone had posted that the solution appeared to be to remove Open SEO Stats from Chrome. When I did, the alerts went away.
A few days ago, I decided to re-enable Open SEO Stats to see what would happen. The URL:Mal alerts did not return. So it would appear as if whatever the problem was with Open SEO Stats has been resolved.
Hope this helps.