Obedient Cat — picoCTF Writeup

Challenge Description

This file has a flag in plain sight (aka "in-the-clear").

The goal is to download the provided file and inspect its contents to find the flag.

Core Concepts (Quick)

File Download

The challenge provides a file that can be downloaded locally for analysis.

Linux cat Command

cat is used to display the contents of a file directly in the terminal.

Plaintext Information

The flag is stored directly inside the file without encryption or encoding.

Step-by-Step Exploitation

Step 1 — Download the File

Download the file provided in the challenge.

After downloading, move to the directory containing the file.

cd Downloads

cd Downloads

Step 2 — Check the File

List the files in the directory:

ls

ls

The downloaded challenge file should be visible.

Step 3 — Read the File

Since the challenge says that the flag is present "in the-clear", simply display the file contents:

cat flag

cat flag

The flag is directly printed in the terminal.

Step 4 — Flag Found

Output:

picoCTF{s4n1ty_v3r1f13d_9b8fa0bc}

picoCTF{s4n1ty_v3r1f13d_9b8fa0bc}

🎉 FLAG CAPTURED

Why This Works

The challenge does not require any exploitation, decoding, or brute-forcing.

The flag is simply stored as plaintext inside the downloaded file. Using the cat command displays the contents directly.

Attack Summary

1. Download the provided file
2. Open the terminal
3. Navigate to the file's directory
4. Use cat to read the file
5. Retrieve the flag

Key Learnings

• Always inspect downloaded files before attempting complex techniques.
• cat is useful for quickly reading text files.
• Challenge descriptions often provide important clues.
• "In-the-clear" means the information is directly readable.

Final Flag

picoCTF{s4n1ty_v3r1f13d_9b8fa0bc}

picoCTF{s4n1ty_v3r1f13d_9b8fa0bc}

Conclusion

The Obedient Cat challenge demonstrates a basic but important CTF skill: always inspect the files you are given.

In this case, the flag was stored directly inside the file, so a simple cat command was enough to solve the challenge.

📬 Stay Connected

If you found this helpful and want to learn more about web security, hands-on labs, feel free to follow me for upcoming posts.

✍️ Follow me for more cybersecurity write-ups 🔗 LinkedIn — codermayank 📸 Instagram — @mayhack_

Tags: #BugBounty #EthicalHacking #ChatGPT #CyberSecurity #AIforSecurity #PenetrationTesting #HackerOne #Bugcrowd #WebSecurity #InfoSec