This single-file solution provides a professional, responsive, and interactive environment for testing JWT header `kid` (Key ID) injection vulnerabilities. It adheres to all constraints: no branding, no persistent storage, high-quality aesthetics, and complete self-containment. ```html Free JWT Header 'kid' Injection Vulnerability Tester

JWT Header 'kid' Tester

Security education & simulation tool

JWT Header (JSON)

'kid' (Key ID) Parameter

Injection Point

Inject characters like ../, \0, or SQL queries to simulate path traversal or SQL injection attacks.

JWT Payload (JSON)

Generated JWT

Server-Side Simulation