Advanced Basic Auth Testing for Bug Bounty

Bug Bounty Tips: Smart Basic Auth Testing (401 Is Not Security)
When you see a Basic Authentication popup and a 401 Unauthorized response, don’t assume the system is secure
In real-world applications, authentication often fails due to simple logic mistakes, not brute force.
A good security tester doesn’t stop at the message - they start analyzing

Phase 1: Test High-Probability Default Credentials​

Always start with default credentials.
They work more often than people like to admit - especially in forgotten admin panels or dev environments.
Common credentials to try:

• test:test
• testassword
• test:admin
• admin:admin
• adminassword
• admin:root

Why this still works​

• Legacy services still running
• Staging or test panels left exposed
• Auto-generated configs never changed
• Development environments pushed to production

These mistakes still exist on live systems and lead to real bug bounty payouts

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Phase 2: Zero-Credential Logic Bypass (Highly Underrated)​

This is the step most testers skip
And sometimes it’s the most critical one.
When the Basic Auth popup appears: Click Cancel and submit NO credentials at all
Why does this matter?
Some backends incorrectly treat:

• Empty Authorization headers
• Missing credentials
• Broken auth states

As valid authenticated sessions

Real-world cases include:​

• Access granted after clicking Cancel
• Backend returning 200 OK with no credentials
• App logic assuming auth was handled by a proxy

This usually happens behind:

• Reverse proxies
• Misconfigured middleware
• Legacy authentication handlers
• Poor error-handling logic

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Practical Testing Using cURL​

Send a request without any Authorization header:

curl -i https://target.com/admin

Send a request with an empty Authorization header:

curl -i -H "Authorization:" https://target.com/admin

Then compare responses with:

• Valid credentials
• Invalid credentials
• Empty credentials
• Canceled authentication

Any behavior difference = potential authentication bypass

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Phase 3: Think Like the Backend, Not the UI​

Always remember

• Browser popup ≠ backend enforcement
• UI denial ≠ server-side denial
• A 401 response is a logic opportunity, not a dead end

Focus on:

• Response headers
• Status codes
• Content length
• Behavior changes

Especially when switching between:

• Valid creds
• Invalid creds
• Empty creds
• No auth at all

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Mindset Shift: Auth Bugs Are Logic Bugs​

Authentication vulnerabilities are rarely about brute force They’re about state confusion
Treat every 401 Unauthorized as:

• A challenge
• A logic puzzle
• A possible bug bounty

Don’t treat 401 as a wall - treat it as a door waiting to open