OPs:
- https://community.norton.com/en/forums/nkkifakvirus-z1x9x-detectedcom-1-844-576-0902
- https://community.norton.com/en/forums/beware-fake-microsoft-windows-activation-attacks
And view this image from MBAM:
Tech Support Scammers use different methods for distributing themselves. This particular one was offered as a PC cleanerb (PC Cleaner Pro), but it also installs files that will produce a fake Windows Activation screen with the Tech Support Scammers number.
As for the said "data:text/...", this Reddit post offers more info: JavaScript. See https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URIs for info re Data URIs.
It's Norton's turn to get ahead of the bad coders.