This writeup is written by HITCON⚔BFKinesiS. We attended DEFCON CTF Qual as an joint team HITCON⚔BFKinesiS (HITCON, Balsn, BambooFox, DoubleSigma and KerKerYuan) this year.
Original writeup (https://balsn.tw/ctf_writeup/20190513-defconctfqual/#return_to_shellql).