Mastering Reconnaissance in Bug Bounty: The Art of Finding Hidden Vulnerabilities

Bug bounty hunting is like digital treasure hunting. The key to success? Strong reconnaissance. Without a proper recon strategy, you’re just shooting in the dark. The best hunters know that information gathering is half the battle won.

In this guide, we’ll explore how to perform effective recon to uncover hidden vulnerabilities and sensitive data leaks.

Step 1: Subdomain Enumeration — Expanding Your Attack Surface

Start by identifying all possible subdomains of your target. Many companies forget about their older or testing environments, which often contain vulnerabilities.

Tools for the Job:

🔹 Amass — Passive and active enumeration
🔹 Subfinder — Quick subdomain discovery
🔹 Assetfinder — Extract assets associated with a domain

Once you have a list, filter out live subdomains with httpx or httprobe. Prioritize endpoints that might expose sensitive files.

Step 2: Finding Sensitive Files and Leaks

Many websites accidentally expose credentials, API keys, or other sensitive files. This is where your file analysis skills come into play.

Where to Look?

✅ /.git/ — Exposed Git repositories containing source code and commit history.
✅ /.git/config — Configuration file of a Git repository, may expose remote repository URLs.
✅ .htaccess — Apache configuration file that can reveal security rules or access restrictions.
✅ /etc/passwd — Linux user account file, which can help enumerate system users (though passwords are usually hashed elsewhere).
✅ composer.json — Dependency manager file for PHP, may reveal framework details and libraries in use.
✅ package.json — Node.js project configuration file, listing dependencies and scripts.
✅ composer.lock — Lock file for PHP dependencies, ensuring exact versions of installed packages.
✅ /.gitattributes — Git attributes file that may reveal repository-specific settings and ignored files.
✅ /.env — Environment file containing API keys, database credentials, and secrets.
✅ /.DS_Store — macOS system file that can expose directory structures and filenames.
✅ /backup/ — Forgotten backup files that might contain database dumps, source code, or old configurations.

Automating the Hunt:

Run GitTools or TruffleHog to check for exposed secrets in repos. You can also use GAU (Get All URLs) to extract URLs and check for misconfigurations.

Pro Tip: While analyzing file extensions, understand how they function. .env files store environment variables, and .git directories can expose commit history—potentially revealing passwords.

Step 3: Crawling & Directory Enumeration

Once you have the domains, it’s time to go deeper. Crawlers and brute-forcing tools help uncover hidden directories.

Tools for the Job:

🔹 ffuf — Fast fuzzing for directories
🔹 dirsearch — Brute-forces directories and files
🔹 waybackurls — Extracts archived URLs

Check for sensitive endpoints like:
🔹 /admin – Admin panels
🔹 /dev – Developer environments
🔹 /debug – Debugging logs

Look for open redirects that could be chained with XSS attacks — your recent study of open redirect vulnerabilities can give you an edge here.

Step 4: OSINT — Gathering Intelligence

Sometimes, the best recon isn’t done on the website itself but in public records. Use Google Dorking and tools like theHarvester to extract emails, credentials, and leaked data from Pastebin or GitHub.

Example Dork:
"site:pastebin.com company_name password"

You might discover exposed credentials, which could lead to account takeovers or internal network access.

Final Thoughts: Think Like an Attacker

Bug bounty recon is about understanding the target’s footprint and looking where others don’t. By combining subdomain enumeration, file analysis, directory brute-forcing, and OSINT, you increase your chances of finding high-impact bugs.

As you dive deeper into bug hunting, remember that your ability to analyze files, extensions, and hidden data leaks is a major advantage. Keep sharpening those skills!