I hacked the “safe” and “unhackable” NumWorks N0120. See this GitHub repo: https://github.com/lukashilverda/numworks-n0120-unlock . With the explanations and the scripts in this repo, it is possible to downgrade the RDP level and upload whatever firmware you want to the calculator. Someone made a bootloader for the N0120 (https://github.com/Dotmazy/Numwork-N120-Crack), and Delta/Upsilon firmware is on the way.

This hack being possible is a big problem for exam integrity. With the possibility to push custom firmware to the calc it is possible to bypass exam mode regulations and do illegal things during exams.