Turns out there’s still more attack surface to cover, as [piraija] tells us in their USB-HID-and-run ... an obscure part of HID standard that defines media buttons, specifically, the “launch ...

[d3ad0ne] came up with a way of dumping files onto an SD card by using the USB HID protocol. We’ve seen this sort of thing before where a microcontroller carries an executable to extract data.