An issue was discovered in certain Apple products. iOS before 11.4 is affected. Safari before 11.1.1 is affected. The issue involves the "Safari" component. It allows remote attackers to cause a denial of service (persistent Safari outage) via a crafted web site.
https://twitter.com/Nate_Kappa/status/1004399403220766725
https://support.apple.com/HT208854
https://support.apple.com/HT208848