Files from Internet zone must be opened in Excel in Protected View mode.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-223340	SRG-APP-000207	O365-EX-000031	SV-223340r961086_rule	2025-03-05	3

Description
This policy setting allows you to determine if files downloaded from the Internet zone open in Protected View. If you enable this policy setting, files downloaded from the Internet zone do not open in Protected View. If you disable or do not configure this policy setting, files downloaded from the Internet zone 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 >> Do not open files from the Internet zone in Protected View 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 DisableInternetFilesInPV is REG_DWORD = 0, this is not a finding. If the value does not exist, this is not a finding. If the value is REG_DWORD = 1, this is a finding.

ℹ️ Check

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Excel 2016 >> Excel Options >> Security >> Trust Center >> Protected View >> Do not open files from the Internet zone in Protected View 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 DisableInternetFilesInPV is REG_DWORD = 0, this is not a finding. If the value does not exist, this is not a finding. If the value is REG_DWORD = 1, this is a finding.

✔️ Fix
Set policy value for User Configuration >> Administrative Templates >> Microsoft Excel 2016 >> Excel Options >> Security >> Trust Center >> Protected View >> Do not open files from the Internet zone in Protected View to "Disabled".