Cheese-chess | 404 CTF 2025

Cheese-chess

Ressources

URL : https://cheese-chess.404ctf.fr/

Exploration

When we go go to the URL, we see a chessboard where we can play.

In the source code, I see this :

<script defer src="/static/js/bundle.js"></script></head>

So when I go to the bundle.js, I saw too many line of code (~ 32 000) so I just do ctrl+f and search for 404CTF{ and I saw the flag.

Exploit

Here a script to auto solve it :

import requests
import re

URL_BUNDLE = "https://cheese-chess.404ctf.fr/static/js/bundle.js"
FLAG_STR_START = "404CTF{"

def grep_flag():
    """
    Fetch the JavaScript bundle from the URL and search for the flag pattern.
    """
    response = requests.get(URL_BUNDLE)
    js_content = response.content.decode('utf-8')

    flag_pattern = re.compile(rf"{FLAG_STR_START}.*?}}")
    match = flag_pattern.search(js_content)

    print(match.group())

grep_flag()