GF_Err payt_Size(GF_Box *s)
{
	GF_PAYTBox *ptr = (GF_PAYTBox *)s;
	s->size += 4;
	if (ptr->payloadString) ptr->size += strlen(ptr->payloadString) + 1;
	return GF_OK;
}

The product reads data past the end, or before the beginning, of the intended buffer.