- using a buffer overflow, we load our own seccomp filter

- with a specific seccomp filter, we bypass glibc's hardening techniques

- we overwrite the secret key stored in memory and get the flag

For a detailed description, follow the link :D

Original writeup (https://github.com/LevitatingLion/ctf-writeups/tree/master/hxp_ctf_2017/pwn_300_hardened_flag_store).