Language: PHP
Label: safe
CWE: CWE-79 \u2014 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
The product 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.

Code:
    public function validate($number, $config, $context)
    {
        $number = $this->parseCDATA($number);

        if ($number === '') {
            return false;
        }
        if ($number === '0') {
            return '0';
        }

        $sign = '';
        switch ($number[0]) {
            case '-':
                if ($this->non_negative) {
                    return false;
                }
                $sign = '-';
            case '+':
                $number = substr($number, 1);
        }

        if (ctype_digit($number)) {
            $number = ltrim($number, '0');
            return $number ? $sign . $number : '0';
        }

        // Period is the only non-numeric character allowed
        if (strpos($number, '.') === false) {
            return false;
        }

        list($left, $right) = explode('.', $number, 2);

        if ($left === '' && $right === '') {
            return false;
        }
        if ($left !== '' && !ctype_digit($left)) {
            return false;
        }

        // Remove leading zeros until positive number or a zero stays left
        if (ltrim($left, '0') != '') {
            $left = ltrim($left, '0');
        } else {
            $left = '0';
        }

        $right = rtrim($right, '0');

        if ($right === '') {
            return $left ? $sign . $left : '0';
        } elseif (!ctype_digit($right)) {
            return false;
        }
        return $sign . $left . '.' . $right;
    }