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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-223343	O365-EX-000034	SV-223343r961092_rule		Medium

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.

STIG	Date
Microsoft Office 365 ProPlus Security Technical Implementation Guide	2025-03-05

Details

Check Text (C-25016r442248_chk)

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 Text (F-25004r442249_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".