bool AbsolutePath(FilePath* path) {
  base::ThreadRestrictions::AssertIOAllowed();  // For realpath().
  char full_path[PATH_MAX];
  if (realpath(path->value().c_str(), full_path) == NULL)
    return false;
  *path = FilePath(full_path);
  return true;
}

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.