Contents

🌐 WebDecode

A detailed write-up of the Web challenge 'WebDecode' from PicoCTF - 2024

/images/PicoGym/PicoCTF-2024/WebDecode/challenge_presentation.png
Challenge Presentation

📊 Challenge Overview

Category Details Additional Info
🏆 Event PicoGym Event Link
🔰 Category Web 🌐
💎 Points Out of 500 total
⭐ Difficulty 🟢 Easy Personal Rating: 1/10
👤 Author Nana Ama Atombo-Sackey Profile
🎮 Solves 49.252 solve rate
📅 Date 28-01-2025 PicoGym
🦾 Solved By mH4ck3r0n3 Team:

📝 Challenge Information

Do you know how to use the web inspector? Additional details will be available after launching your challenge instance.

🎯 Challenge Files & Infrastructure

Provided Files

1
Files: None

🔍 Initial Analysis

First Steps

Initially, the website appears as follows:

/images/PicoGym/PicoCTF-2024/WebDecode/site_presentation.png
Site Presentation

By navigating the website through the navbar and visiting the About page, I obtained this:

/images/PicoGym/PicoCTF-2024/WebDecode/flag_page.png
Flag Page

As the website itself suggested, I inspected the page using ChromeDevTools and found a strange Base64 string:

/images/PicoGym/PicoCTF-2024/WebDecode/base64_flag.png
Base64 Flag

🎯 Solution Path

Exploitation Steps

Initial setup

Once the Base64 string was found, the exploit was solely based on decoding it.

Exploitation

I decoded it directly using bash, with the base64 command combined with echo:

1
  echo cGljb0NURnt3ZWJfc3VjYzNzc2Z1bGx5X2QzYzBkZWRfMTBmOTM3NmZ9 | base64 -d; echo "\n"

Flag capture

/images/PicoGym/PicoCTF-2024/WebDecode/manual_flag.png
Manual Flag

🛠️ Exploitation Process

Approach

The exploit makes a request to the page and uses bs4 to extract the flag in Base64, then decodes it and prints it.

🚩 Flag Capture

Flag

Proof of Execution

/images/PicoGym/PicoCTF-2024/WebDecode/automated_flag.png
Automated Flag
Screenshot of successful exploitation

🔧 Tools Used

Tool Purpose
Python Exploit

💡 Key Learnings

Skills Improved

  • Binary Exploitation
  • Reverse Engineering
  • Web Exploitation
  • Cryptography
  • Forensics
  • OSINT
  • Miscellaneous

📊 Final Statistics

Metric Value Notes
Time to Solve 00:00 From start to flag
Global Ranking Challenge ranking
Points Earned Team contribution

Created: 28-01-2025 • Last Modified: 28-01-2025 *Author: mH4ck3r0n3 • Team: *