Security issues after authenticated user has been logged out
Once page is stored in browser's cache, there is nothing you can do about it. It's responsibility of an user who logs in and views confidential information to remove it from device he was reading it on. 

You could try to prevent caching (as described in this question), but all you send to browsers and proxies in that regard is just an suggestion, not an order. It's a good idea to do this, but sadly you can't be sure of it.

You could use javascript to go to another page if logged out user tries to go back to page with sensitive data.

And you can and should use Secure Pages to enforce encryption and thus prevent proxies from reading you data.

At the end of the day once user will get that data, data security is his problem.