Greetings 7benw,
We're happy to help out today in Apple Support Communities.
It sounds like you have a pop-up you aren’t able to get past when using Safari on your Mac. Which macOS version is installed? That’s found by going to Apple menu > About This Mac.
When you say a new version of Safari, do you mean you updated your macOS? We want to be sure we are understanding since that’s the only way to update Safari.
Since this is a message appearing that you can’t get rid of, take a look at Recognize and avoid phishing messages, phony support calls, and other scams. It’s good to read the entire article, but in this case look at the section “If your web browser displays annoying pop-ups”. If you don’t have Malwarebytes there is a free option available for Macs that will scan to see if you have anything infecting your compute now. Just scroll midway down to see the free version.
Reach back out if we can help further.
Have a great weekend!