This is a continuation of a discussion here:
http://drupal.org/node/17190
I've opened a new thread due to some confusion regarding the title of the thread above, which has kinda taken away from the importance of the subject.
Firstly, I think it is important to set the scope of this problem. This is not about problems with setting up a drupal site behind a proxy firewall, and having problems with RSS and the like. There are many issues that have been discussed about that, and I believe the patches supplied address this issue adequately ( http://drupal.org/node/9706 )
The general problem is this:
1) For an end user accessing a Drupal based site through a proxy firewall, pages they are shown may not be the most current page
2) Pages that are rendered by the proxy may even be protected versions of the page that were recently accessed by another user with escalated privelleges.
3) when dealing with node level access control, nodes that have been recently changed from 'public' to 'private' (for lack of better terms) may still be available to a user who shouldn't have access to them.
The problems this access causes are varied. In my cases, dealing more with node level access control issues, since the pages were being rendered with their public status intact, it also meant the form elements for making them private weren't being rendered properly - this inadvertantly had the effect of making the real version of the page public once again because the user failed to realize that the checkmark was not checked in the cached version.