Now the question is if there is a exploit in the rom and by crafting your own audio you can make the device much more interesting.
Actually, here's a guide: https://learn.adafruit.com/dash-hacking-bare-metal-stm32-pro...
How do they know for sure? Perhaps they also connect every month for a (status) update or for statistics, but this hacker just missed that.
I wouldn't use these buttons to launch any missiles :)