{
  "claim_outcome": "no_bypass_found",
  "claim_block_reason": null,
  "repro_result": "no_variant",
  "validated_surface": "library_api",
  "evidence_scope": "isolated_harness",
  "claimed_impact_class": "dos",
  "observed_impact_class": "none_no_bypass",
  "exploitability_confidence": "low",
  "attacker_controlled_input": "email header keys including __proto__, __PROTO__, constructor, prototype",
  "trigger_path": "Header.parse() -> _add_header() with prototype pollution keys",
  "end_to_end_target_reached": true,
  "sanitizer_used": true,
  "crash_observed": false,
  "read_write_primitive_observed": false,
  "exploit_chain_demonstrated": false,
  "blocking_mitigation": "Object.create(null) removes prototype chain; explicit guards block __proto__, constructor, prototype keys",
  "inferred": false,
  "variant_tests_conducted": 5,
  "variant_tests_failed": 0,
  "bypass_tests": [
    {
      "variant_name": "original __proto__",
      "result": "blocked",
      "notes": "Guard explicitly returned before accessing headers object"
    },
    {
      "variant_name": "uppercase __PROTO__",
      "result": "blocked",
      "notes": "toLowerCase() normalization converts to __proto__, then blocked by guard"
    },
    {
      "variant_name": "constructor",
      "result": "blocked",
      "notes": "Guard explicitly returned before accessing headers object"
    },
    {
      "variant_name": "prototype",
      "result": "blocked",
      "notes": "Guard explicitly returned before accessing headers object"
    },
    {
      "variant_name": "add() method entry point",
      "result": "blocked",
      "notes": "All paths route through guarded _add_header() method"
    }
  ],
  "conclusion": "After testing 5 distinct variants against the fixed version (v1.3.2), no bypass was found. The fix uses defense-in-depth with Object.create(null) and explicit key guards, covering all tested entry points and key manipulation strategies. The fix is comprehensive for this attack vector."
}