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Require API Auth, Validation, and Tenant Scoping

Flags API endpoints that skip auth, trust client-supplied tenant or account IDs, accept unvalidated request bodies, or leak internal errors.

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What it flags

Flaggedapp/api/projects/route.ts
import { db } from '@/lib/db';

export async function POST(req: Request) {
  const body = await req.json();

  // No session check, no validation, and the client picks the organization
  const project = await db.project.create({
    data: {
      name: body.name,
      organizationId: body.organizationId,
    },
  });

  return Response.json(project);
}
Passesapp/api/projects/route.ts
import { z } from 'zod';

import { getSession } from '@/lib/auth';
import { db } from '@/lib/db';

const CreateProject = z.object({
  name: z.string().trim().min(1).max(100),
});

export async function POST(req: Request) {
  const session = await getSession();
  if (!session) {
    return Response.json({ error: 'Unauthorized' }, { status: 401 });
  }

  const parsed = CreateProject.safeParse(await req.json().catch(() => null));
  if (!parsed.success) {
    return Response.json({ error: 'Invalid request body' }, { status: 400 });
  }

  const project = await db.project.create({
    data: { name: parsed.data.name, organizationId: session.organizationId },
  });
  return Response.json(project, { status: 201 });
}

Why it matters

Cross-tenant data leaks usually come from a handler that reads an organization or account ID from the request and queries by it without checking that the caller belongs to it. The handler works in every happy-path test because the tester uses their own IDs. Missing validation has the same shape: the endpoint accepts whatever JSON arrives, and malformed or malicious input reaches the database or a downstream service.

Agent instructions

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AGENTS.md

Add this section to AGENTS.md at the repository root. Codex, Cursor, and other AI coding tools read it.

## Require API Auth, Validation, and Tenant Scoping

Review API handlers and controller endpoints for missing authentication, authorization, tenant scoping, and request validation.

Flag new or modified endpoints that:
- Accept request bodies without runtime validation, such as Zod schemas, DTOs, or framework-native validators.
- Trust user-supplied identifiers for tenant, organization, or account access instead of deriving access from the authenticated session.
- Return sensitive internal errors or use inconsistent HTTP status codes for 400, 401, 403, 404, and 500 cases.
- Mix reads and writes in a way that makes side effects hard to reason about.
- Add public or high-volume endpoints without rate limiting or abuse controls.

Checks every changed file.

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Included in the Next.js, TypeScript, Node.js, Python, Django, Ruby on Rails, Go, and Spring Boot code review standards.

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Catch this in your code