The IDOR Bug Cursor Keeps Writing Into Your API Routes
AI-generated code often lacks proper authorization checks, leading to Insecure Direct Object Reference (IDOR) vulnerabilities where any logged-in user can access or modify another user's data.
Why it matters
IDOR is one of the most common vulnerabilities in web applications, and AI-generated code is prone to producing it, putting user data at risk.
Key Points
- 1AI editors add authentication middleware but routinely skip ownership checks
- 2Result: IDOR (CWE-639) -- any logged-in user can read or modify another user's data
- 3Fix: one condition verifying resource.userId === req.user.id before returning data
Details
AI-powered code editors like Cursor, Claude Code, and Copilot are trained on examples that separate authentication from authorization. While they add authentication middleware to protect routes, they often neglect the crucial step of verifying that the authenticated user owns the requested resource. This leads to IDOR vulnerabilities, where any logged-in user can access or modify data that doesn't belong to them. The fix is simple - add a single condition to check if the resource's user ID matches the authenticated user's ID before returning the data.
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