The ubiquitous ESP32 microchip made by Chinese manufacturer Espressif and used by over 1 billion units as of 2023 contains an undocumented "backdoor" that could be leveraged for attacks.

Update 3/9/25: After receiving concerns about the use of the term "backdoor" to refer to these undocumented commands, we have updated the title of our story.

https://www.bleepingcomputer.com/news/security/undocumented-commands-found-in-bluetooth-chip-used-by-a-billion-devices/