Security Warning: The current Web page is trying to open a site on your intranet

Question:

Why are we seeing the Security Warning pop-up in IE saying "The current Web page is trying to open a site on your intranet."?

Environment: Cisco Web Security appliance (WSA) in transparent proxy deployment and authentication is enabled using the single word, short hostname.

Symptoms: When transparently proxying traffic and using authentication, Internet Explorer prompts with with following error (as seen in the screenshot)

------------------------------------------------------------------------------------ :

Security Warning: The current Web page is trying to open a site on your intranet.
Do you want to allow this?

Current Site: www.whatever.com
Intranet site: <WSA hostname>

------------------------------------------------------------------------------------



Note: This Knowledge Base article references software which is not maintained or supported by Cisco.  The information is provided as a courtesy for your convenience. For further assistance, please contact the software vendor.

Internet Explorer may prompt when authentication is enabled in a transparent proxy environment, due to the fact that it believes a public website is redirecting to an intranet server. This is technically called "Zone Elevation". This behavior can be controlled via the Internet Explorer configuration.

Follow the steps below to prevent Internet Explorer from prompting in this case:

Disabling the Zone Elevation Security Warning

1. Click on 'Tools' -> 'Internet Options' -> 'Security' tab -> 'Local Intranet' 2. Click the 'Custom Level' button 3. Towards the bottom, find 'Websites in less privileged web content zone can navigate into this zone'. 4. Set this option to 'Enable'.