Introduction

JavaScript files are often overlooked during web application testing, yet they can reveal a wealth of sensitive information and lead to critical security vulnerabilities. From API endpoints and secret tokens to logic flaws and client-side vulnerabilities, JavaScript is a goldmine for bug bounty hunters and security researchers. This guide walks you through the step-by-step process of identifying, analyzing, and exploiting JavaScript files for maximum impact.

1. Why JavaScript Files Matter in Bug Hunting

JavaScript is responsible for rendering dynamic content, handling API communication, and storing various client-side configurations. Since developers often hard-code information or expose sensitive logic, analyzing these files can reveal:

• Hidden API endpoints
• Environment variables and keys
• Authentication flows
• Internal paths and functions
• Sensitive comments and test/debug logic