IE5 ACL protected pages viewable from cache by unauthorized user

[krobinson () TEAMLEX COM (J.Kent Robinson)]

Running IIS4 on NT4 (SP5) server.  Several web pages have 
permissions assigned with NT ACL (both NT Challege/Response 
and Basic Authentication).  Discovered that protected pages 
can be viewed by unauthorized user (presumably from cache) 
if authorized user previously accessed pages from same 
computer client.  This happens even after the browser has 
been completely closed and then reopened.  An unauthorized 
user accesses the page by hitting the page link.  This 
brings up the pop-up logon window.  Hit cancel.  User gets 
a 401 screen.  Hit the back button.  Hit the forward 
button.  Viola . . . the user without credentials has 
access to the protected content.  I've tested this behavior 
on NT4 WS, Win98 and Win2000 clients with the same 
results.  Posts at the MS newsgroups yielded little 
response.