[cssom-1] add empty security & privacy section

Author: svgeesus

cssom-1/Overview.bs

@@ -3246,6 +3246,11 @@ Changes From 12 July 2011 To 5 December 2013 {#changes-from-12-july-2011-to-5-de
  <li>The <a method for=CSS lt=escape()>CSS.escape()</a> static method is introduced.
 </ul>
 
+Security and Privacy Considerations
+===================================
+
+No new security or privacy considerations have been reported on this specification.
+
 
 Acknowledgments {#acknowledgments}
 ==================================