Did you try the meta tags?
<meta content="0" http-equiv="EXPIRES"></meta> <meta content="NO-CACHE" http-equiv="PRAGMA"></meta> <meta content="NO-CACHE" http-equiv="CACHE-CONTROL"></meta>
Yes I did. Were you able to solve this problem?
Back- and forward-navigation between 'secure' pages will only be restricted after logging out if you have specify the page property login-required="true" for those pages you do not want the browser to cache in memory.
For example (in pages.xml):
<page view-id="/homepage.xhtml" login-required="true"> ... </page>
If you log-out from a page (or pages) that does(do) not have this attribute set to true you will be able to navigate back and forth which is the correct behaviour IMHO.