[gigel82]

Interesting... lots of devices (industrial control, PBXs, even smart thermostats, etc.) have debug Tx/Rx pins with no authentication at all.

We have very small ESP32 boards so plug those in, find a power pin (most controllers will have a 5v/3.3v with headroom enough for esp32 to work) and bam, you're in.

Reminds me of the Raspberry Pi in a thermostat episode from Mr. Robot (but that needed a lot more power and was physically larger)