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($string, $config, $context)
    {
        $allowed = array('false');
        if ($config->get('HTML.Trusted')) {
            $allowed = array('', 'true', 'false');
        }

        $enum = new HTMLPurifier_AttrDef_Enum($allowed);

        return $enum->validate($string, $config, $context);
    }