{
  "same_root_cause": true,
  "confidence": "high",
  "parent_root_cause": "Pre-fix AttachmentService.save_upload_file trusted multipart UploadFile.filename and joined it into a temporary filesystem path before writing and unlinking.",
  "variant_candidate_root_cause": "An absolute multipart filename exploits the same missing path-confinement invariant because pathlib temp_dir / absolute_path discards temp_dir before temp_path.open('wb').",
  "same_sink": "server/services/attachment_service.py::AttachmentService.save_upload_file",
  "same_trust_boundary": "Unauthenticated HTTP multipart filename reaching POST /api/uploads/{session_id}; variant runtime exercised the sink directly after parent RCA established route-to-sink reachability.",
  "difference_from_parent": "Parent used POSIX ../ traversal segments; variant candidate used absolute filenames and preexisting/symlink targets.",
  "fix_coverage_result": "Fixed/latest commit blocks both parent and absolute filename forms with basename normalization.",
  "bypass_confirmed": false
}