Fender Mustang GT 100 guitar amplifier acts as a Bluetooth device without authenticating the connection. Anyone with a smartphone can feed it any sound or music and the amplifier takes the order without question. The problem is amplified by the fact that the device is also intended for live performances. Unless Bluetooth is disabled before a live gig, anyone in the audience could connect to the amp and turn the performance into a private party. Until Fender releases a patch that adds at least basic authentication over Bluetooth, researchers recommend guitarists disable this connection when they are not using it.”]
Source: https://www.bitdefender.com/blog/hotforsecurity/bluetooth-can-cause-fender-bender-guitar-amp/