The plan:

* Create a chunk > 0x408 and free it to send to unsorted bin and leak libc.
* Use 'off by one' bug to change next chunk size.
* Now you can overwrite the forward pointer of the other next chunk with __free_hook

Original writeup (https://github.com/GonTanaka/CTF-Writeups/upload/main/Cyber_Apocalypse2022/pwn/Bon-nie-appetit).