PicoCTF Writeup – where are the robots

Information: 

CTF Name: PicoCTF

CTF Challenge: where are the robots

Challenge Category: Web Exploitation

Challenge Points: 100

PicoCTF 2019.

# Challenge Description: 

Can you find the robots? https://jupiter.challenges.picoctf.org/problem/56830/ or http://jupiter.challenges.picoctf.org:56830

Writeup 

By reading the description of the challenge I found interesting the question “Can you find the robots?”. So I went online and searched for what are robots in the context of web applications. And I come across this

In this document, it is possible to read about the file robots.txt and learn a little about what this file actually is. It seems that this file is used to inform the crawler mechanisms which pages/archives can be requested to the site.

Knowing this I went to the link supplied in the description and searched for the file “robots.txt” as you can see in the image below: 

Link

 
The contents of the site are presented in the image below:
 
In the image above, we have this line “Disallow: /1bb4c.html”. This is the only file available in the robots.txt. It is worth trying to go to this file, so I inserted the following link in the browser:
 
 
The contents of the site are presented below:
 
 
As you can see in the image above in this file (1bb4c.html) we have the flag.
 
And the flag is:
 
Show flag
picoCTF{ca1cu1at1ng_Mach1n3s_1bb4c}

The image source can be found here.

Thank you very much for reading!

Cheers,

MRegra

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