CTF Challenge: flagAreStepic

May 31, 2025 PicoCTF Medium

Challenge Overview

  • The following was the description for the challenge: stepic challenge

Approach

  • So if you go through the provided link.
    stepic challenge

  • From here, went straight to the source code. stepic challenge
  • After scrolling and trying to understand the source code.
  • There was only one line that looked suspicious. stepic challenge
  1. Analysis of image:Immediately i thought of image steganography, So i tried to save the image first. stepic challenge
    • From here, as you can see, i wanted to confirm if the image exists in the URL 🙏. stepic challenge
  2. Detail Analysis: From here, it just a matter of transferring the file from the local machine to the virtual machine(Kali Linux).

stepic challenge

  • Normally, i hate it when i have a png files, because the skills that i know about image steganography, are only limited to JPEG files. The steghide tool is only applicable for JPEG but not for PNG’s.
    • So what now?
    • After numerous attempts!…i finally decided to look at the hint.

      stepic challenge
  • The hint did not help much, but it did help with verification, that the image that i found was actually suspicious.
  • I looked at the meta data again, i saw that the image size(14173x10630) is so insanely high, like that is not normal for an ordinary image especially in this case, a flag. So definitely there is something hidden in the image.
  • Again, because of the limited knowledge, i still struggled.
  • As always, i had to make a research on what tools are used for retrieving information from a PNG file.
  • You can check out my notes for more information regarding the tool I found or just click the following link, it should take you to my notes: forensics-stepic.
  • But yeah, apparently there is a specific tool for PNG’s, and it also does not work for JPEG’s 😆.
  • And it is easy to use.

  1. Flag:
    stepic challenge