Rating: 5.0

We are given a website that lets us add a format string that is passed to `date` command.

First what we see is a banner:

> Proudly coded with Vim editor

We check address `` and get some version of `index.php` file. Here we see that there is a file `varflag.php` which holds a flag.

Back to the form. The command we send is escaped, but as a whole, so if we could interfere with outside world with `date` arguments only, we could probably do something. Reading manual tells that option `-f` allows to read format strings from file. We send ` -f varflag.php` (space is to separate format string from the `-f` argument), view source (so that `'

privat – Oct. 8, 2017, 9:07 p.m.

Please remove/blank the writeup, the CTF is still running.

Zubek – Oct. 8, 2017, 11:13 p.m.

Hello Sir,

Please explain how you have found it.