Looks like this is an ongoing Google ads problem, but it apparently only hitting people in the US, AFAICT. The working fix for the moment seems to be is block Google ads, AdSense, AdMob, DoubleClick. Getting things like fake virus warnings, dating, pr0n, redirects to the Play Store, gambling, offshore pharmacies, penis & muscle growth pills, etc.
I m not in U.S , I m from Pakistan. I tried Adblock but no use. Only temporary fix is clearing data but that destroys all my bookmarks and opera mobile isn't synchronized anywhere.
I will investigate today. But all I know is that it gets started when I open online forums lie XDA, this forum and my local country forums