Add "no-store" to Cache-Control header to prevent history caching of admin resources

[soulseekah]

The current implementation of ​wp_get_nocache_headers does not take into account history caching, which results in a browser serving a cached copy of pages from history (by pressing the Back button) even if the user has long logged out.

​RFC 2616 14.9.2 no-store describes this cache directive.

To repoduce: login to dashboard, logout, press the back button.
Expected: the login screen.
Reality: a copy of the previous page.

By adding the "no-store" directive to all non-cachable resources the behavior was mitigated successfully in Chrome 21, Firefox 15. Fails on Opera 12 (they chose to disregard "no-store" when applied to history, RFC allows this).

[soulseekah]

"no-store" please

[toscho]

That needs good tests. For example the ​behavior after POST requests can be quite annoying. Performance might be an issue too.

[soulseekah]

Replying to toscho:

That needs good tests. For example the ​behavior after POST requests can be quite annoying. Performance might be an issue too.

Agreed, under certain circumstances this could be a nuisance, especially if users are logged in and the admin bar is shown. As for performance, it seems that all of twitter is served with "no-store" and it does appear (to me) to be quite jagged navigation-wise.

Without a proper step-by-step testing plan in mind, I guess I'll use the patch in production for a bit to see if it causes any unexpected issues in general.

[nacin]

The other issue is sometimes you want the back button to be where you were last, without a complete reload. How many times have you lost a comment or some other content by clicking away (in WP or not) and scrambled to recover it?

[johnbillion]

Related: #19444.

[nevma]

It seems that Firefox actually needs the no-store as well, in order to not cache a page. Otherwise, it serves it from the ​BFCache. The no-store should be added to the wp_get_nocache_headers function in the Cache-Control header. This is what the ​MDN documentation in Using Firefox Caching mentions, too.

[dingo_bastard]

Is this something that will be implemented or not? Since there exists a nocache_headers filter, if user wants to modify the Cache-Control all he/she has to do is unset it and then add no-store in it with the filter.

IMO this ticket can be closed.

[vikram6]

Hi. Are there any plans to fix this or should we workaround it on our side?

[johnbillion]

Moving to 6.3 along with #57627

[johnbillion]

#57938 was marked as a duplicate.