undefined

misc/undefined

Description

I was writing some Javascript when everything became undefined... Can you create something out of nothing and read the flag at /flag.txt? Tested for Node version 17.

Downloads: index.js

Solution

For this challenge we are given a js script that reads our input and then calls eval on it. Before doing so, it sets almost all global functions to undefined. After some experimenting, I realized that import could still be used. All I had to do at this point is to import fs and read the flag:

import('fs').then(fs => fs.readFile('/flag.txt', 'utf8', (err, data) => {console.log(data, err)}));

I'm quite sure that this solution is not the intended one but it still gives the flag: dice{who_needs_builtins_when_you_have_arguments}.