A Practical Guide to Uncovering Hidden Vulnerabilities in Modern Signup Systems
Press enter or click to view image in full size
Introduction
Hi everyone, Welcome back! Today, we’re looking into one of the most critical parts of any application: the signup flow. This is the ‘front door’ where user input first hits the database and authentication layer, which makes it a goldmine for bugs. I’m talking about everything from simple logic flaws to critical vulnerabilities.
In this article, I’m going to break down the essential checks I always do when testing registration features. These are practical, battle-tested steps straight from my pentesting methodology to help you spot the vulnerabilities that usually go unnoticed.
Table of Contents
Table of Contents1. Introduction
2. Duplicate Registration and Account Overwrite
3. Case Sensitivity and Shadow Account Bypass
4. Denial of Service Through Large Input Fields
5. Missing Rate Limiting During Signup
6. Stored XSS in Registration Fields
7. Weak or Broken Email Verification
8. Unsafe Registration Practices (HTTP, Temp Emails)
9. Weak Password Policies
10. Path Overwrite and Route Collision
11. Server-Side Validation Bypass
12. Hidden or…