이쪽 참고 해서 파일을 수정해주셔야 합니다.

/kbaord/helper/Security.helper.php 파일 하단에 아래 클래스를 추가해주시고

kboard_xssfilter() 함수에 설정을 추가 해주세요.

$HTMLPurifier_Config->set('Filter.Custom', array(new HTMLPurifier_Filter_MyIframe()));

/**
 * Based on: http://sachachua.com/blog/2011/08/drupal-html-purifier-embedding-iframes-youtube/
 * Iframe filter that does some primitive whitelisting in a somewhat recognizable and tweakable way
 */
class HTMLPurifier_Filter_MyIframe extends HTMLPurifier_Filter
{
    public $name = 'MyIframe';

    /**
     *
     * @param string $html
     * @param HTMLPurifier_Config $config
     * @param HTMLPurifier_Context $context
     * @return string
     */
    public function preFilter($html, HTMLPurifier_Config $config, HTMLPurifier_Context $context)
    {
        $html = preg_replace('#<iframe#i', '<img class="MyIframe"', $html);
        $html = preg_replace('#</iframe>#i', '</img>', $html);
        return $html;
    }

    /**
     *
     * @param string $html
     * @param HTMLPurifier_Config $config
     * @param HTMLPurifier_Context $context
     * @return string
     */
    public function postFilter($html, HTMLPurifier_Config $config, HTMLPurifier_Context $context)
    {
        $post_regex = '#<img class="MyIframe"([^>]+?)>#';
        return preg_replace_callback($post_regex, array($this, 'postFilterCallback'), $html);
    }

    /**
     *
     * @param array $matches
     * @return string
     */
    protected function postFilterCallback($matches)
    {
        // Domain Whitelist
        $youTubeMatch = preg_match('#src="https?://www.youtube(-nocookie)?.com/#i', $matches[1]);
        $vimeoMatch = preg_match('#src="http://player.vimeo.com/#i', $matches[1]);
        if ($youTubeMatch || $vimeoMatch) {
            $extra = ' frameborder="0"';
            if ($youTubeMatch) {
                $extra .= ' allowfullscreen';
            } elseif ($vimeoMatch) {
                $extra .= ' webkitAllowFullScreen mozallowfullscreen allowFullScreen';
            }
            return '<iframe ' . $matches[1] . $extra . '></iframe>';
        } else {
            return '';
        }
    }
}