A bug discovered by Mac Magazine allows users to access hidden messages on an iPhone just by asking Siri to read them aloud. Apple has long allowed users to hide their notification previews in Messages — displaying only that a new message was received and keeping the contents private until the device was unlocked, and more recently extended this capability to third-party apps. The bug — spotted in both iOS 11.2.6 and the beta of iOS 11.3 — doesn’t…