Unsigned add-ins in PowerPoint must be blocked with no Trust Bar Notification to the user.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-223384	SRG-APP-000131	O365-PT-000008	SV-223384r1016170_rule	2025-03-05	3

Description
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 the "Require that application add-ins are signed by Trusted Publisher" policy setting is enabled, which prevents users from changing this policy setting. If this policy setting is enabled, applications automatically disable unsigned add-ins without informing users. If this policy setting is disabled, 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 this policy setting is not configured, 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.

Description

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 the "Require that application add-ins are signed by Trusted Publisher" policy setting is enabled, which prevents users from changing this policy setting. If this policy setting is enabled, applications automatically disable unsigned add-ins without informing users. If this policy setting is disabled, 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 this policy setting is not configured, 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.

ℹ️ Check
Verify the policy value for User Configuration >> Administrative Templates >> Microsoft PowerPoint 2016 >> PowerPoint 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\powerpoint\security If the value notbpromptunsignedaddin is REG_DWORD = 1, this is not a finding.

ℹ️ Check

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft PowerPoint 2016 >> PowerPoint 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\powerpoint\security If the value notbpromptunsignedaddin is REG_DWORD = 1, this is not a finding.

✔️ Fix
Set the policy value for User Configuration >> Administrative Templates >> Microsoft PowerPoint 2016 >> PowerPoint Options >> Security >> Trust Center "Disable Trust Bar Notification for unsigned application add-ins and block them" to "Enabled".