Safari 12 & CAC Authentication

We are aware of an issue with Safari 12 where users are unable to access CAC-protected websites.
 
The problem is that Safari never prompts the user to enter a PIN.  After a few moments, the following error will appear:
 

Safari Can’t Open the Page

Safari can’t open the page “(website)”. The error is:
“WebKit encountered an internal error” (WebKitErrorDomain:300)
 
The only known workaround is to use Google Chrome.  Chrome can be downloaded from www.google.com/chrome.
 
When we have further information, we will update this document.
 
Update:
 
We have tested Safari 12.0 on macOS Mojave and have found that v12.0 (14606.1.36.1.9) should be able to use your CAC or PIV.  macOS High Sierra has v12.0 (13606.2.11) and it is not prompting for certificates.  We will continue to watch for Safari updates, and will update this FAQ with any new information.
 
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Safari 12 was released September 17, 2018
This page updated October 4, 2018