iPhone aficionados at iDeviceHelp and EverythingApplePro have discovered yet another way for someone who has physical access to your phone to access your messages, photos, and contacts. The hack uses Siri to activate the VoiceOver feature on the target phone while the phone is still locked. The flaw affects any iDevice that can receive Facetime or phone calls. There is an easy way to prevent this from happening: disable Siri access on the lockscreen. If you cant use Siri to enable VoiceOver, this hack (and many others) will not work.”]
Source: https://nakedsecurity.sophos.com/2016/11/18/iphones-vulnerable-to-yet-another-lockscreen-bypass/