Safari tab says "Your device has been infected with 21 viruses"

I had launched safari on my iPhone 11 and seen that I had a tab that said:

Critical threat

Your device has been infected with 21 viruses after visiting an Adult website.

If the problem is not resolved immidiately: viruses will damage your device, harm the SIM card and delete all your contacts.

To protect your device from the viruses, click the button "Remove all viruses" below, install AV Blocker app from the AppStore, open it and run clearing procedure

Remove all viruses

System Damage

To check system damage click "Check your device" below, install AV Blocker app from the AppStore, open it and run scanning procedure

Check your device

the website that had this page is: ***

is this legit or just them wanting me to get some app???

[Edited by Moderator]