CVE-2013-6271
Android 4.0 through 4.3 allows attackers to bypass intended access restrictions and remove device locks via a crafted application that invokes the updateUnlockMethodAndFinish method in the com.android.settings.ChooseLockGeneric class with the PASSWORD_QUALITY_UNSPECIFIED option.
Date published : 2013-12-14
http://seclists.org/fulldisclosure/2013/Nov/204
http://www.theregister.co.uk/2013/12/10/android_has_lockbypass_bug/