Visio must automatically disable unsigned add-ins without informing users.
This policy setting controls whether the specified Office application notifies users when unsigned application add-ins are loaded or silently disable such add-ins without notification. This policy setting only applies if you enable the "Require that application add-ins are signed by Trusted Publisher" policy setting, which prevents users from changing this policy setting. If you enable this policy setting, applications automatically disable unsigned add-ins without informing users. If you disable this policy setting, if this application is configured to require that all add-ins be signed by a trusted publisher, any unsigned add-ins the application loads will be disabled and the application will display the Trust Bar at the top of the active window. The Trust Bar contains a message that informs users about the unsigned add-in. If you do not configure this policy setting, the disable behavior applies, and in addition, users can configure this requirement themselves in the "Add-ins" category of the Trust Center for the application.
Set the policy value for User Configuration >> Administrative Templates >> Microsoft Visio 2016 >> Visio Options >> Security >> Trust Center >> Disable Trust Bar Notification for unsigned application add-ins and block them to Enabled.
Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Visio 2016 >> Visio Options >> Security >> Trust Center >> Disable Trust Bar Notification for unsigned application add-ins and block them is set to Enabled. Use the Windows Registry Editor to navigate to the following key: HKCU\software\policies\microsoft\office\16.0\visio\security If the value notbpromptunsignedaddin is REG_DWORD = 1, this is not a finding.