function test($serialized) {
  $ret = null;
  var_dump(
    fb_unserialize(
      $serialized,
      inout $ret,
      FB_SERIALIZE_HACK_ARRAYS
    )
  );
  var_dump($ret);
}
The product does not properly control the amount of recursion which takes place,  consuming excessive resources, such as allocated memory or the program stack.