Bluetooth in Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-07-01 allows local users to gain privileges by establishing a pairing that remains present during a session of the primary user, aka internal bug 27410683.
https://android.googlesource.com/platform/system/bt/+/37c88107679d36c419572732b4af6e18bb2f7dce