I just signed up to give you a heads up on what I've uncovered. I'm also getting the issue on iOS Chrome and Safari. I was browsing the Guardian newspaper's website (reputable, not at all likely to be a cause for issue) and as soon as I scrolled down to an AdChoices ad that auto-displayed I got the popup which auto redirected to the site in question. It appears to me that YET again, malvertising (malicious ads) have penetrated Google's system and have poisoned every website they touch (attacking customers at random). Basically the ads have some dodgy scripting inside that pushes that alert on you and redirects you away to their fake page hoping you'll get scammed out of cash. This is why advertising is such a terrible way for sites to make money, especially when they outsource the responsibility for who serves the ads to third parties who don't properly sanitize them for dangerous scripts like browser hijacking.