static bool StartsHTMLOpenCommentAt(const String& string, size_t start) {
  return (start + 3 < string.length() && string[start] == '<' &&
          string[start + 1] == '!' && string[start + 2] == '-' &&
          string[start + 3] == '-');
}

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.