An issue was discovered in certain Apple products. iOS before 11.3 is affected. macOS before 10.13.4 is affected. tvOS before 11.3 is affected. watchOS before 4.3 is affected. The issue involves the "NSURLSession" component. A race condition allows attackers to execute arbitrary code in a privileged context via a crafted app.
https://support.apple.com/HT208698
https://support.apple.com/HT208696
https://support.apple.com/HT208693
https://support.apple.com/HT208692