File validation in Excel must be enabled.

Severity
Group ID
Group Title
Version
Rule ID
Date
STIG Version
mediumV-223334SRG-APP-000112O365-EX-000025SV-223334r960921_rule2025-03-053
Description
This policy setting allows you turn off the file validation feature. If you enable this policy setting, file validation will be turned off. If you disable or do not configure this policy setting, file validation will be turned on. Office Binary Documents (97-2003) are checked to see if they conform against the file format schema before they are opened.
ℹ️ Check
Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Excel 2016 >> Excel Options >> Security >> Turn off file validation is set to "Disabled". Use the Windows Registry Editor to navigate to the following key: HKCU\software\policies\microsoft\office\16.0\excel\security\filevalidation If the value for enableonload is REG_DWORD = 1, this is not a finding.
✔️ Fix
Set policy value for User Configuration >> Administrative Templates >> Microsoft Excel 2016 >> Excel Options >> Security >> Turn off file validation to "Disabled".