Opera confirmed Wednesday that its latest browser, 8.01, would display the pop-up's origin, letting a user inspect its URL to see if it came from a trusted site.

A Proofpoint spokesperson said the popup box instructed people to paste text into a PowerShell terminal or Windows Run dialogue box.

"The problem is that JavaScript dialog boxes do not display or include their origin, which allows a new window to open — for example, a prompt dialog box — which appears to be from a trusted ...