> Looking at the images here, there is zero attempt at security here from the ledger team. They’re using an MCU (ST MCU with Cortex M4 core) that doesn’t have any meaningful security features (ie, no secure boot, no differentiation between trusted and user mode operation - features the newer Cortex M33 core supports and newer ST parts implement).

That MCU is explicitly not assumed to be critical in their security model [1]. It handles Bluetooth and USB communication, both of which are assumed to be insecure transport layers. Securing the MCU would not have helped in this particular incident, and I can't think of a scenario in which it would be critical.

Button input and screen output, which are critical, are handled by a secure element. Unfortunately, at some point even the most hardened secure element will have to output data to be displayed on a screen; that's what was attacked here. Electronic shoulder surfing, basically.

[1] https://www.ledger.com/ledger-nano-x-bluetooth-security-mode...