This is an issue in the 2023.003.20269 update.

I use an application that generates HTML documents with PDF files linked inside them. An IE frame is used to preview HTML, which allows the Adobe Add On to preview the PDF inside of the page. The PDF files are stored on a network drive with the path to the file being a UNC path.

When opening the file in IE Adobe throws an error:

Cannot Access the URL:

UNC PATH

Security Restrictions Prohibit Access To Untrusted URLs.

Disabling the security measures within Adobe make no difference or adding the UNC as a trusted location. I have also updated the PDF source to a URL instead of a UNC path and this then loads fine, so it's only an issue with UNC paths.

I have downgraded back to 2023.003.20244 where this is not an issue.