CVE-2021-39880: apollo_upload_server has Denial of Service vulnerability

The vulnerability stems from improper array index handling in the GraphQL data builder. The commit diff shows the vulnerable version used 'field[splited_path.last.to_i] = wrapped_file' without validation. The patched version adds strict index validation (verify_array_index!) and integer parsing (parse_array_index) to prevent out-of-bounds writes. The HackerOne report demonstrates how crafted 'map' parameters with large indices could force the server to generate massive error responses, confirming this function's role in the vulnerability.