- Unrestricted file upload when creating books
- Bypass the extension filter to get a PHP webshell

[**Full Writeup**](https://ctf.zeyu2001.com/2021/yauzactf-2021/yauzacraft-pt.-2)

Original writeup (https://ctf.zeyu2001.com/2021/yauzactf-2021/yauzacraft-pt.-2).