Youtuber videosdebarraquito found a major bug in the new iOS 9. With his finding, a user can access a phone’s messages and photos while the phone is still ‘locked’ through Siri.
To bypass the lock, just enter an incorrect passcode four times. After four attempts, enter three numbers and hold down the home button to bring up Siri. From Siri, you can get to messages, photos, and contacts.
To prevent this from happening to your phone, just disable Siri while locked. To do this, go to Settings -> Touch ID & Passcode and scroll down to Allow access when locked.