Last month, while testing a “secure” fintech app, I discovered an unprotected Firebase database leaking OAuth tokens, bank account links, and transaction histories — all because of one misconfigured API endpoint. The company paid me $300 after I demonstrated how an attacker could drain thousands of accounts. Here’s the full technical breakdown, with actual cURL commands and Python scripts I used.

free link

“If you don’t get a ‘403 Forbidden’, you’re probably onto something.”

Most API breaches happen due to:

• Missing access controls (No auth checks)
• Excessive data exposure (Returning entire user objects)
• Debug endpoints left open (like /api/v1/test/admin)

Step 1: Intercepted Mobile App Traffic

• Used Burp Suite to proxy the app’s requests
• Found a call to:

GET https://fintech-app.firebaseio.com/users.json?auth=null  

Step 2: Tested for Public Access