circsay

Simple shell injection CTF problem

Install

Requirements: Docker, git

git clone https://github.com/TCIRC/circsay.git
cd circsay
./run.sh

Solution

1. `ls` to print directory contents
2. `cat flag.txt`; echo a to print flag and escape cowsay
3. flag.txt is cow language to output the flag, google cow language online and paste the code into the first search result
4. the flag is FLAG{why_u_rce_my_machine_u_bad_bad_guy_sub_to_nekomata_okayu_now}