| Full Fuzzer Name | HttpParameterPollutionFieldsFuzzer |
| Log Key | HPPFF |
| Description | Duplicates query parameters in the request URL with conflicting second values (for example ?status=ACTIVE&status=catsPolluted) to detect HTTP Parameter Pollution (HPP) and array-coercion crashes. |
| Enabled by default? | Yes (included in security, ci, crash, and full profiles) |
| Target field types | URL query parameters |
| Expected result when fuzzed field is required | 4XX or 2XX |
| Expected result when fuzzed field is optional | 4XX or 2XX |
| Expected result when fuzzed value is not matching field pattern | 4XX or 2XX |
| Fuzzing logic | Iterates through declared query parameters and appends a duplicate query parameter with a conflicting value (catsPolluted for strings, -999999 for numbers, or the opposite boolean). |
| Conditions when this fuzzer will be skipped | When the operation declares no query parameters. |
| HTTP methods that will be skipped | HEAD, TRACE |
| Reporting | Reports error on 5XX server errors or unexpected status codes; reports success on 4XX or 2XX matching the contract. |