The Android Client application, when enrolled to the AppHub server, connects to an MQTT broker to exchange messages and receive commands to execute on the HMI device. The protocol builds on top of MQTT to implement the remote management of the device is encrypted with a hard-coded DES symmetric key, that can be retrieved reversing both the Android Client application and the server-side web application. This issue allows an attacker able to control a malicious MQTT broker on the same subnet network of the device, to craft malicious messages and send them to the HMI device, executing arbitrary commands on the device itself.