static void zend_throw_or_error(int fetch_type, zend_class_entry *exception_ce, const char *format, ...) /* {{{ */
{
	va_list va;
	char *message = NULL;

	va_start(va, format);
 	zend_vspprintf(&message, 0, format, va);
 
 	if (fetch_type & ZEND_FETCH_CLASS_EXCEPTION) {
		zend_throw_error(exception_ce, "%s", message);
 	} else {
 		zend_error(E_ERROR, "%s", message);
 	}

	efree(message);
	va_end(va);
}
/* }}} */

The product uses a function that accepts a format string as an argument, but the format string originates from an external source.