/*
 * This is an example of how to override a default filter
 * for 'textarea' sanitization and $allowedposttags + embed and script.
 */
add_action('admin_init','optionscheck_change_santiziation', 100);

function optionscheck_change_santiziation() {
    remove_filter( 'of_sanitize_textarea', 'of_sanitize_textarea' );
    add_filter( 'of_sanitize_textarea', 'custom_sanitize_textarea' );
}

function custom_sanitize_textarea($input) {
    global $allowedposttags;
    $custom_allowedtags["embed"] = array(
      "src" => array(),
      "type" => array(),
      "allowfullscreen" => array(),
      "allowscriptaccess" => array(),
      "height" => array(),
          "width" => array()
      );
      $custom_allowedtags["script"] = array();

      $custom_allowedtags = array_merge($custom_allowedtags, $allowedposttags);
      $output = wp_kses( $input, $custom_allowedtags);
    return $output;
}