I highly recommend https://microcorruption.com/ https://microcorruption.com/ - it was a game by (the now defunct) Matasano to do hiring for exploit researchers,

I highly recommend https://microcorruption.com/ https://microcorruption.com/ - it was a game by (the now defunct) Matasano to do hiring for exploit researchers, and is a lot of fun. You're given the disassembly for an ARM e-lock and told to craft an exploit to gain access.