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Last Updated: April 3, 2024

ISSUE

When you click to open an .ICS file you are prompted with the following warning: 

“Microsoft Office has identified a potential security concern.

This location may be unsafe.”

Outlook blocks .ics files

This issue happens after installing the Outlook Desktop December 12th security updates. For additional information see the respective CVEs. CVE-2023-35636 - Security Update Guide - Microsoft - Microsoft Outlook Information Disclosure Vulnerability

STATUS: FIXED

This issue is fixed in Version 2404 Build 17531.20000+ estimated to release to Current Channel on 4/30/24. The Outlook Team will backport the fix to Version 2402 for Semi-Annual Enterprise Channel (Preview) after the fix has been in production. Version 2402 will go to Semi-Annual Enterprise Channel on patch Tuesday, 7/9/2024.

The fix is at the Beta Channel with build 17531.20000+ and will go to Current Channel Preview once it updates to 17531.20000+. Please use the Office Insider Channels to test and verify the fix.

In the meantime, if you need to temporarily disable the security notice you can use the registry key below. If you decide to use the registry key, please be aware it will stop security notice prompts for all types of files and not just for the .ICS files.

If you need to disable this dialog, follow the instructions in the article Enable or disable hyperlink warning messages in Office programs.

Group Policy registry path:

HKEY_CURRENT_USER\software\policies\microsoft\office\16.0\common\security
DWORD: DisableHyperlinkWarning
Value: 1

OCT registry path:

Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Security
DWORD: DisableHyperlinkWarning
Value: 1

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See Also

Fixes or workarounds for recent issues in Outlook for PC

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