That interface doesn’t have to be special, and [Dakhnod] is here to show us that it can be done with an ESP32 microcontroller through its USB interface. The linked repository doesn’t tell us ...

It is communication that traditionally runs via UART or SPI protocols ... "Backdoor in ESP32? Not so fast. Yes, hidden HCI commands allow deep access to memory, flash and Bluetooth internals.

A hot potato: The ESP32 chip, found in over a billion devices ... to manipulate memory by reading and writing to RAM and Flash, spoof MAC addresses to impersonate devices, and inject LMP/LLCP ...