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Received an alarm & pop up for me to call 877-563-5714 to fix a serious security issue, not to restart computer. Is this a scam?

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I was browsing & received an audible alarm. I found a pop up that read: Dear Customer, A serious malfunction has been detected with Windows 10 & your Firefox 49.0.Please call the toll-free number below for a Microsoft -Certified Technician to help you resolve the issue. 877-563-5714 For your safety, closing the Firefox browser has been disabled without support of the Microsoft-Certified technician to avoid corruption to the registry of your Windows 10 64-bit operating system...DO NOT SHUT DOWN OR RESTSRT THE COMPUTER.DOING THAT MAY LEAD TO DATA LOSS AND POSSIBLE FAILURE OF THE OPERATING SYSTEM AND POTENTIAL NON BOOTABLE SITUATION RESULTING IN COMPLETE DATA LOSS... and it repeats in a pop up

I was browsing & received an audible alarm. I found a pop up that read: Dear Customer, A serious malfunction has been detected with Windows 10 & your Firefox 49.0.Please call the toll-free number below for a Microsoft -Certified Technician to help you resolve the issue. 877-563-5714 For your safety, closing the Firefox browser has been disabled without support of the Microsoft-Certified technician to avoid corruption to the registry of your Windows 10 64-bit operating system...DO NOT SHUT DOWN OR RESTSRT THE COMPUTER.DOING THAT MAY LEAD TO DATA LOSS AND POSSIBLE FAILURE OF THE OPERATING SYSTEM AND POTENTIAL NON BOOTABLE SITUATION RESULTING IN COMPLETE DATA LOSS... and it repeats in a pop up

Chosen solution

I'm pretty sure that's a scam. Can you get rid of that page using any of these methods:

  • Esc key (cancels certain dialogs, resizes pages that go full screen using a script)
  • Ctrl+w (close tab shortcut)
  • Ctrl+F4 (close document shortcut)
  • Alt+F4 (close window shortcut)
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Chosen Solution

I'm pretty sure that's a scam. Can you get rid of that page using any of these methods:

  • Esc key (cancels certain dialogs, resizes pages that go full screen using a script)
  • Ctrl+w (close tab shortcut)
  • Ctrl+F4 (close document shortcut)
  • Alt+F4 (close window shortcut)