An issue was discovered in certain Apple products. iOS before 11.3 is affected. macOS before 10.13.4 is affected. The issue involves the "WindowServer" component. It allows attackers to bypass the Secure Input Mode protection mechanism, and log keystrokes of arbitrary apps, via a crafted app that scans key states.
https://twitter.com/boastr_net/status/979624397664333824
https://support.apple.com/HT208693
https://support.apple.com/HT208692
http://www.securitytracker.com/id/1040608