security notification

Recognize and avoid phishing messages, phony support calls, and other scams

https://support.apple.com/en-us/HT204759

About pop-up ads and windows in Safari

https://support.apple.com/en-us/HT203987

Delete spam calendars and events on iPhone

https://support.apple.com/en-us/HT211076

It’s probably calendar spam. See→Delete spam calendars and events on iPhone - Apple Support

Is that a calendar event notification? Can you describe what it states? Thanks.

Axel F.