Information
This policy setting allows administrators to disable all trusted locations in the specified applications. Trusted locations specified in the Trust Center are used to define file locations that are assumed to be safe. Content, code, and add-ins are allowed to load from trusted locations with a minimal amount of security, without prompting the users for permission. If a dangerous file is opened from a trusted location, it will not be subject to standard security measures and could harm users' computers or data. If you enable this policy setting, all trusted locations (those specified in the Trust Center) in the specified applications are ignored, including any trusted locations established by Office 2016 during setup, deployed to users using Group Policy, or added by users themselves. Users will be prompted again when opening files from trusted locations. If you disable or do not configure this policy setting, all trusted locations (those specified in the Trust Center) in the specified applications are assumed to be safe. The recommended state for this setting is: Enabled. Trusted locations specified in the Trust Center are used to define file locations that are assumed to be safe. Content, code, and add-ins are allowed to load from trusted locations with a minimal amount of security, without prompting the users for permission. If a dangerous file is opened from a trusted location, it will not be subject to standard security measures and could harm users' computers or data. By default, files located in trusted locations (those specified in the Trust Center) are assumed to be safe.
Solution
To implement the recommended configuration state, set the following Group Policy setting to Enabled. User Configuration\Administrative Templates\Microsoft Excel 2016\Excel Options\Security\Trust Center\Trusted Locations\Disabled all Trusted Locations Impact: If there are business-critical reasons to access some files in a more trusted environment, disabling trusted locations could cause usability problems.