    public static function id($userid){
        $usr = Db::result(
            sprintf("SELECT * FROM `user` WHERE `userid` = '%s' LIMIT 1", 
                Typo::cleanX($userid)
                )
            );
        return $usr[0]->id;
    }

The software constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component.