ZEND_API int clean_non_persistent_function_full(zval *zv) /* {{{ */
{
	zend_function *function = Z_PTR_P(zv);
	return (function->type == ZEND_INTERNAL_FUNCTION) ? ZEND_HASH_APPLY_KEEP : ZEND_HASH_APPLY_REMOVE;
}
/* }}} */

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