As others have said here, you are using Norton so it will occasionally popup with parts of Norton that you are not using, wanting you to install them, hence pushing you by saying that you haven't installed it yet.
The easiest way to not have the popup appearing is to simply just install the Norton Safe Web extension and then simply disable it in Safari.
See Also
FAQ: Alerts and notificationsSee here for disabling it in various web browsers.
https://support.norton.com/sp/en/us/home/current/solutions/v45748162
You can also have a read of this thread too from Norton Support and try it.
https://community.norton.com/en/comment/8533712#comment-8533712
I do not subscribe, so please do not always expect a reply.
