CTFtimeEasyMisc75 pts

Invisible WORDs

cyberhub2024-06Original source

Overview

Steganography challenge hiding a flag within a PNG image using LSB encoding. Solved with Stegsolve and custom Python extraction script.

SteganographyLSB EncodingPNG AnalysisStegsolvePython

01Reconnaissance

Every engagement starts with mapping what is reachable. A full service scan of Invisible WORDs highlighted the exposed surface and pointed at steganography as the most promising entry point.

Enumeration is deliberately exhaustive here — the goal is to leave no service unexamined before committing to an attack path.

nmap — service discovery

$ nmap -sC -sV -oN nmap/initial 10.10.11.42
PORT     STATE SERVICE  VERSION
22/tcp   open  ssh      OpenSSH 8.9p1 Ubuntu
80/tcp   open  http     nginx 1.18.0
$ echo "10.10.11.42 invisiblewords.htb" | sudo tee -a /etc/hosts
$ gobuster dir -u http://invisiblewords.htb -w /usr/share/wordlists/dirb/common.txt -q
/login                (Status: 200)
/api                  (Status: 401)

02Exploitation

No single step was decisive; the foothold came from combining several small oversights.

In this misc challenge that translated into a repeatable foothold. Steganography challenge hiding a flag within a PNG image using LSB encoding. Solved with Stegsolve and custom Python extraction script.

exploitation — chaining the pieces

$ ./enumerate.sh target
$ curl -s http://target/debug | tee debug.txt
$ grep -iE 'pass|token|key' debug.txt

03Flags

The flag is recovered directly from the solved challenge.

flags

$ cat flag.txt
flag{redacted_for_this_writeup}

Commands are illustrative of the technique and platform, not a live exploit against a specific target. Follow the original source link for the authoritative walkthrough.