    protected function forwardUntilEndToken(&$i, &$current, &$nesting) {
        $result = $this->forward($i, $current);
        if (!$result) return false;
        if ($nesting === null) $nesting = 0;
        if     ($current instanceof HTMLPurifier_Token_Start) $nesting++;
        elseif ($current instanceof HTMLPurifier_Token_End) {
            if ($nesting <= 0) return false;
            $nesting--;
        }
        return true;
    }
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.