Disallowed but Discoverable: The Hacker’s robots.txt Playbook

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Ever felt like a pirate on the hunt for hidden treasure? 🏴‍☠️ As bug bounty hunters, we’re all about uncovering the secrets others try to bury. But what if I told you the most overlooked and underestimated file on any website — the humble robots.txt—could be your treasure map?

That’s right! This seemingly innocuous file, designed to guide search engine crawlers, often holds breadcrumbs leading to sensitive directories, confidential endpoints, or even forgotten functionality. While most see it as harmless, seasoned hackers know it can be a goldmine for reconnaissance.

In this guide, I’ll show you how to go beyond the basics of robots.txt, leveraging its full potential to find vulnerabilities, access restricted areas, and report impactful bugs. By the end, you'll have the tools and mindset to turn this unassuming file into a valuable ally in your bug bounty journey.

Outline of the Story:

1. What is robots.txt?

• A brief explanation of robots.txt:

It’s a plain text file in the root directory of a website that tells search engine bots which parts of the site they can and cannot crawl.

• Examples of typical entries:

User-agent: *  
Disallow: /admin/  
Disallow: /internal-api/

• Why it matters for bug bounty hunters:
• Reveals restricted areas.
• Highlights forgotten endpoints.
• Provides insight into site structure.

2. How to Find and Analyze robots.txt

Locating the file:

Accessing robots.txt is simple—just append /robots.txt to any domain.
Example: https://example.com/robots.txt

• Analyzing entries:

Look for /admin, /backup, /staging, /test, /api, or other sensitive directories.

Watch for references to outdated or forgotten systems.

• Example Analysis:

User-agent: *  
Disallow: /backup/  
Disallow: /api/legacy/

• These entries may lead to directories that are poorly secured or…