1. Read a line from `output.txt`
2. Take the first 8 characters of it, and transform them from hex into their ASCII codes
3. XOR those 4 characters with one of 256 possible ASCII codes
4. If we find that this equals `CHTB`, we've found our line and key
5. Decrypt our line with our key

Original writeup (https://kblagoev.com/blog/wild-goose-hunt-cyberapocalypse-2021-ctf/).