Phishing
I got phishing message on my imac by clicking a picture on safari. command-Q does not work to remove it. Let me know how to get rid of it.
iPhone 8 Plus, iOS 13
Sometimes all you'd need would be clear history in the browser, and restart.
A settings item should provide the ability to do this. Other things to try:
Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support
//support.apple.com/en-us/HT204759
Block pop-up ads and windows in Safari - Apple Support
//support.apple.com/en-us/HT203987
(+avoid interacting with popups)
In iOS settings, in Safari browser details, you can change them
to clear History; that works to fix the issue. Repeat as needed.
Other things to discover may require looking deeper into Apple
User Guides, maybe for Safari. These overlap to varying degree.