File attachments from Outlook must be opened in Excel in Protected mode.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-223343	SRG-APP-000210	O365-EX-000034	SV-223343r961092_rule	2025-03-05	3

Description
This policy setting allows you to determine if Excel files in Outlook attachments open in Protected View. If you enable this policy setting, Outlook attachments do not open in Protected View. If you disable or do not configure this policy setting, Outlook attachments open in Protected View.

ℹ️ Check
Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Excel 2016 >> Excel Options >> Security >> Trust Center >> Protected View >> Turn off Protected View for attachments opened from Outlook is set to "Disabled". Use the Windows Registry Editor to navigate to the following key: HKCU\software\policies\microsoft\office\16.0\excel\security\protectedview If the value DisableAttachmentsInPV is REG_DWORD = 0, this is not a finding.

ℹ️ Check

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Excel 2016 >> Excel Options >> Security >> Trust Center >> Protected View >> Turn off Protected View for attachments opened from Outlook is set to "Disabled". Use the Windows Registry Editor to navigate to the following key: HKCU\software\policies\microsoft\office\16.0\excel\security\protectedview If the value DisableAttachmentsInPV is REG_DWORD = 0, this is not a finding.

✔️ Fix
Set policy value for User Configuration >> Administrative Templates >> Microsoft Excel 2016 >> Excel Options >> Security >> Trust Center >> Protected View >> Turn off Protected View for attachments opened from Outlook to "Disabled".