MetaCTF CyberGames 2020


This will be a short but sweet writeup. You can find a backup of the challenge here on my GitHub in case you don’t have access to it.

The challenge is simply to extract some data from a PDF file.

When you open the PDF you are presented with this:


Knowing this, it looked like there is just an image or drawing over what we want to see, so I did some research to find a suitable program to disassemble the PDF.

I stumbled upon mutools which I installed in Kali:

pt install mupdf-tools

While the tutorial I was following had some complicated steps to get what I was looking for, I simply gave

mutool extract cybercorp_memo.pdf

This gave me the following image:

The embedded image

And the follwing flag:


And that’s it! Just knowing the right tool for the job makes it pretty easy.