Virus

The battery issue has nothing to do with a scam popup. It's just a scam, like getting a scam phone call saying you'll be placed under arrest for failing to appear for jury duty unless you pay the crook some made up fee. The popup is just words. It can't do anything to your device.

You need a new battery is all that means.

It's a scam. A message warning of malware will only be legitimate if you manually started a scanner or uploaded a file to a website.

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