XDA Developers discovered that Android 7.1 ships with a panic mode that is triggered by repeatedly pressing the back button for times in a row. Once this panic mode is activated, the device is brought back to the desktop, closing every app that’s running and bypassing any further locks.
The panic detection system works with a grace time of 0.3 seconds per tap, as Android needs to detect whether the user is indeed trying to activate this feature or only pressing the back button to go to a previous screen or app.
