    public function validate($string, $config, $context) {
        $string = trim($string);
        if (!$this->case_sensitive) {
            // we may want to do full case-insensitive libraries
            $string = ctype_lower($string) ? $string : strtolower($string);
        }
        $result = isset($this->valid_values[$string]);

        return $result ? $string : false;
    }
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.