A hands-on tutorial for building a deliberately vulnerable Node.js/Express lab that demonstrates the mass assignment vulnerability. Starting from GitHub repo setup, it walks through creating a simple web app with user registration, then intentionally introduces the flaw by spreading req.body into a user object — allowing an attacker to override the role field and gain admin access. The post explains why the spread operator causes the vulnerability, why database defaults don't protect against it, and how to fix it by explicitly destructuring only expected fields.
Table of contents
Mass AssignmentGithubCreating the Lab’s SkeletonLab StructureBoilerplate CodeGet ShadowForge ’s stories in your inboxWhat Matters In This CodeMaking The Mistake (Deliberately)Why It WorksFixing The Mistake396 Impressions