URL category warning pages are delayed up to 90 seconds after the configuration is committed

Question:

1. Why does the URL categpry warning page not show up immediately for certain websites?
2. If URL category warning is enabled while users are still browsing, then the warning page may not be displayed on the browser for up to 90 seconds?

Environment: Cisco Web Security Appliance (WSA), All AsyncOS versions

Symptoms:

• Immediately after enabling the 'Warn' policy action, certain browsers and web sites will not display the warning page for up to 90 seconds
• If the Warning policies are enabled while users are currently browsing, the warning page may not be displayed on the browser for up to 90 seconds.

Example:
A user is browsing to a website, like cnn.com, when the "News" category is set to "Warn" in access policies. If the user continues to browse without closing the browser, the website - cnn.com - will not show the "Warning" page for about 90 seconds after the change was committed.

The problem typically happens when the website data/information is cached by the browser. When the content is 'cached' by the browser, the browser would server the data directly from cache and no request would be made via the WSA proxy, thus causing the 'Warning' page to not be displayed.

In this case, if the user/s clicks on the browser's refresh button, the warning page will be displayed properly. Additionally if the browser's cache is cleared and the page is re-requested, it will also display the warning page.

Note: This behavior does not happen for all websites and browsers. Most websites will show the warning page immediately after the WSA is configured to 'Warn'.