Testing API for Mass Assignment Vulnerability

When to Use

• Testing API endpoints that accept JSON/XML request bodies for user profile updates, registration, or object creation
• Assessing whether the API binds all client-supplied properties to the data model without an allowlist
• Evaluating if users can set privileged attributes (role, permissions, pricing, balance) through regular update endpoints
• Testing APIs built with ORMs that auto-bind request parameters to database models
• Validating that server-side input validation restricts writeable properties per user role

Do not use without written authorization. Mass assignment testing involves modifying object properties in potentially destructive ways.

Prerequisites

• Written authorization specifying target API endpoints and scope
• Test accounts at different privilege levels
• API documentation or OpenAPI specification to identify expected request fields
• Burp Suite Professional for request interception and parameter injection
• Python 3.10+ with requests library
• Knowledge of the backend framework (Rails, Django, Express, Spring) to predict parameter binding behavior