void CreateTextFile(const FilePath& filename,
                    const std::wstring& contents) {
  std::wofstream file;
  file.open(filename.value().c_str());
  ASSERT_TRUE(file.is_open());
  file << contents;
  file.close();
}

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.