First spotted by Jose Rodriguez, who last September found a similar flaw in iOS, and highlighted by The Daily Dot, Apple's mobile operating system contains a vulnerability that lets others access your Contacts and Photos using Siri on the Lock screen of your iPhone 6s, bypassing your passcode.
Fortunately, there's an easy fix for this which involves revoking Siri access to Twitter and Photos and disabling Lock screen access to the personal digital assistant. Apple has not commented on the bug, which will likely be squashed in an upcoming software update.