Issue with Windows 10 IoT Enterprise Keyboard Filter

Question

I'm creating an image using Windows 10 IoT Enterprise LTSC 2019. We have a default user on the machine that has a custom WPF shell, and a Keyboard Filter enabled to prevent the user from breaking out of the shell. The filter seems to work as expected for the most part, but it seems that the user is able to circumvent the filter with the Application/Menu/Context key - the key that's next to right control on some keyboards. If the user presses the Context key with a filtered key, and then releases the context key, they're able to use key combinations using that filtered key. For example:

With a key filter for Alt, Context -> Alt + Context -> release Context -> Alt + Space: brings up the standard Alt + Space dialog.

This also allows the user to Ctrl+Alt+Delete, which we don't want to allow either, since they will be able to run explorer. We've also tried rebinding the Alt key to Control in the registry, but the Context key will still circumvent that. I was also unable to get the Context key to be filtered using the Keyboard Filter and it doesn't appear to be in any of the official documentation.

Does anyone have advice on how to solve this?

EDIT: Update - we were also able to generate this behavior with Windows+Alt, using the same process as above.

Answer 1

Rather than using a PowerShell script, I create a couple of Free Keyboard filter utilities to control the state of the keyboard filter. These utilities can help diagnose the issue:

1. What type of account is the default user? Administrator or User.
2. If administrator, what do you have the option to "Disable Keyboard filter for administrators" set to?
3. Is the Keyboard Filter service enabled?
4. Is the "Application" key set to be blocked?