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Your JWT Is Valid. Your Spring Boot API Is Still Leaking Data.
A production-grade guide to object-level authorization, IDOR, multi-tenant security, and preventing users from accessing one another’s records
Reading time: Approximately 30 minutes Technology stack: Java, Spring Boot 3, Spring Security 6, JWT, Spring Data JPA, PostgreSQL, JUnit 5, and MockMvc Level: Intermediate to advanced backend engineering
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1. The Security Bug That Survives Code Review
Imagine you are building an order management application using Spring Boot.
Customers can log in, view their orders, download invoices, cancel eligible purchases, and track deliveries. Authentication is implemented using Spring Security and JWT. Every protected endpoint requires a valid access token.
The security team reviews the implementation. The application validates JWT signatures, checks expiration, configures stateless sessions, and rejects unauthenticated requests.
The application goes to production.
A customer opens their order history and sees a request like this:
GET /api/orders/10042 HTTP/1.1
Host: api.example.com
Authorization: Bearer eyJhbGciOiJIUzI1NiJ9...The API returns the order.
