[judge2020]

Even if it does handle delivering firmware updates to the device, I would be wholly surprised if the terminal doesn't at least do basic checks to make sure the firmware is signed (although, whether or not there are exploits to get around this is another thing).

[MBCook]

The devices I’ve seen all have signed firmware.

[avianlyric]

Yeah the firmware should be signed and have an EMV certification. It’s a total pain in the arse to develop and deploy new software for these devices.