It's a scam popup. Usually some infected ad server. Not your PC, phone, tablet or smart device.
Using FF 54.0 64 bit in Linux Mint, I will get a skeletonized box with the following message inside:
Logon To Your Account
Shopping Account shopdaddy.co.in
The upper right side has small box with an X and also a triangle underneath that a mouse-over produces something about AdChoices. (I do use Adblock plus but it's partially disable for Cnet.) There is a forward facing arrow in a circle that, when clicked on, produces a "RansomWare Alert" message as well as audio claiming that if you close the box without calling the number given your Microsoft account will be disabled. Closing the message produces the following;
"http://microsoftsupportlinehelp.com is requesting your username and password. The site says: “0x80070424 Microsoft Security Alert: Ransomeware Threat Detected !!! Call Microsoft Help Desk: +1-800-683-9841 (TOLL-FREE) ”
The audio message also makes reference to "Error 268B3" which is an easy Google away from finding others who have reported this. What makes it go away for me is to change AdBlock plus to block Cnet ads entirely. Interestingly as well, without blocking Cnet this way, I will get an offer using the same size and shaped skeletonized box offering a password finder for $9.99.
This has been happening today only and only when I boot Linux and not Windows. I suspect this is not caused by a malicious program that's been installed on my machine but by a malicious ad that runs on the Cnet site as this only happens here. I'll keep an eye on it.