From youtuber.com. I get this pop up most of the time when I go there, they just take it down for a little and change their number whenever they get flooded. The link can lock your browser.
Link: hxxp://safari-ios-error.us/ios-apple.com-safari-error-number0101334abfrd500101010101010101010101010101010101010/t7.html
Number: +1-844-804-3949