How to get notication from website to stop

So, today I opened up my mac and started to receive notifications in my notification widget tab for this site. I have never been to their site or anything, and it's saying something about a virus scan. How can I stop this from popping up again? 

I tried searching for it in my safari settings, applications, and computer settings. 

This is a photo of the notifcation that pops up.

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