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:
            trigger_error(
                '%Attr.IDPrefixLocal cannot be used unless ' .
                '%Attr.IDPrefix is set',
                E_USER_WARNING
            );
        }

        if (!$this->selector) {
            $id_accumulator =& $context->get('IDAccumulator');
            if (isset($id_accumulator->ids[$id])) {
                return false;
            }
        }

        // we purposely avoid using regex, hopefully this is faster

        if ($config->get('Attr.ID.HTML5') === true) {
            if (preg_match('/[\t\n\x0b\x0c ]/', $id)) {
                return false;
            }
        } else {
            if (ctype_alpha($id)) {
                // OK
            } else {
                if (!ctype_alpha(@$id[0])) {
                    return false;
                }
                // primitive style of regexps, I suppose
                $trim = trim(
                    $id,
                    'A..Za..z0..9:-._'
                );
                if ($trim !== '') {
                    return false;
                }
            }
        }

        $regexp = $config->get('Attr.IDBlacklistRegexp');
        if ($regexp && preg_match($regexp, $id)) {
            return false;
        }

        if (!$this->selector) {
            $id_accumulator->add($id);
        }

        // if no change was made to the ID, return the result
        // else, return the new id if stripping whitespace made it
        //     valid, or return false.
        return $id;
    }