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 transform($attr, $config, $context)
    {
        $lang = isset($attr['lang']) ? $attr['lang'] : false;
        $xml_lang = isset($attr['xml:lang']) ? $attr['xml:lang'] : false;

        if ($lang !== false && $xml_lang === false) {
            $attr['xml:lang'] = $lang;
        } elseif ($xml_lang !== false) {
            $attr['lang'] = $xml_lang;
        }
        return $attr;
    }