Block loading of COM/VSTO add-ins registered in HKCU

Description

This policy setting controls whether COM/VSTO add-ins registered only in HKEY_CURRENT_USER (HKCU) are blocked from loading. Standard users can install add-ins through ClickOnce deployment or the Office Add-ins settings, which typically register add-ins in HKCU rather than HKEY_LOCAL_MACHINE (HKLM). If you enable this policy setting, all COM/VSTO add-ins registered only in HKCU will be blocked from loading, preventing users from running add-ins they have installed without administrator privileges. If you disable or don't configure this policy setting, COM/VSTO add-ins registered in HKCU are allowed to load normally. Note: Add-ins registered in HKLM (typically installed by administrators) are not affected by this policy setting.