Source from hacker news: http://money.cnn.com/2015/09/16/technology/android-hack/index.html
Note: It only affects smartphones using the latest version of the Android operating system, Lollipop.
Locked phones require a passcode. But there’s a way to get around that.
Just type in an insanely long password. That overloads the computer,
which redirects you to the phone’s home screen.
It’s basically a game of copy-and-paste.
From the locked screen, open the phone’s “Emergency Call” feature. Type a
few characters, then copy-and-paste the text repeatedly. The character
“string” grows exponentially, so it quickly becomes close to 40,960
characters long.