A vulnerability has been discovered in Android operating systems v 5.0 through v 5.1.1 “LMY48M”, the security issue allows an attacker to bypass the lock screen and gain full access to a locked device. Discovered by researchers at the University of Texas the issue got reported, and thankfully the Android security team released an update a few months ago in June which fixes the problem.
Android devices on older builds ( v 5.0 through v 5.1.1) of the operating-system are still vulnerable to the attack as shown in the "step by step" demonstration video as shared below. The attack involves entering a large string of characters into the password field which is used to crash the lock-screen in order to gain unrestricted access to the device bypassing the password security.