Your mobile web browser (which does not allow any sort of ad-blocking, despite running on a phone I paid for and using bandwidth I continue to pay for) allows malvertisements to lock out the "back" button.
Happened this morning. I'm pretty sure the malvertisement in question came over your ad network, under whatever name.
Ya know, a naive user would be stuck there until he tapped on the nice friendly download some malware to "fix" this "problem" button.
And, ya know what else? Your browser leaks information like a sieve hoop. There's no fargin' reason an ad should be able to determine the model number of the phone I'm using. None. Window size, yes. Details of the phone, no way. Now I'm wondering what other information can be fetched from the browser. Bank login credentials, perhaps? (No, I'm not fool enough to log onto my bank from my phone, but some people evidently are.)