When using Chrome on my Nexus 6, I often get taken to a data URI that causes a modal that reads something like:
An embedded page at s3.amazonaws.com says: Message! Congratulations Grande Communications user, you have been chosen for a chance to get a new iPhone.... Click OK to continue
There is no Cancel button. Why does Google allow developers to launch pop-ups with no cancel button?
This doesn't occur from clicking on a link. Usually it happens while I'm on a tab, and suddenly another tab will spawn with the modal. I don't think it's caused by a visit to a dubious host, because it's happened when I've had only top sites (Amazon, ebay, etc.) open in the other tabs.
I have run Malwarebytes and a few other security tools and they all say my phone is secure and clean.
What exactly is happening? On the standard Chrome browser, web extensions can rewrite URLs but Chrome for mobile doesn't have web extensions. Could an app intercept network calls from the browser? Could the sites I'm visiting just be serving malicious ads?