MC1125497 – (Updated) External workbook links to blocked file types will be disabled by default

Product:

Microsoft 365 Apps

Platform:

Mac, Online, World tenant

Status:

Change type:

Admin impact, New feature, Updated message, User impact

Links:

Details:

Summary:
External workbook links to blocked file types were going to be disabled by default starting November 2025, but this change is currently on hold. Administrators can control this via group policy or registry settings. Existing links retain last values but won’t refresh; new links return a #BLOCKED error.

Details:
Updated November 25, 2025: This change is currently on hold. We will communicate via Message center when we are ready to proceed. We apologize for any inconvenience this may have caused and thank you for your patience.
Introduction
To enhance workbook security, a new group policy is being introduced to expand File Block Settings to external workbook links. This policy allows administrators to control whether links to blocked file types can be refreshed.
If not configured, no changes will take effect immediately. However, starting November 2025, the default behavior will block external links to file types currently blocked by the Trust Center. When this policy is enabled, new references to blocked file types will return a #BLOCKED error. Existing links will display the last successfully refreshed values but will no longer refresh.
When this will happen
General Availability: We will update this Message center post when we are ready to proceed.

Change Category:
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Scope:
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Release Phase:

Created:
2025-07-31

updated:
2025-11-26

Task Type

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Docu to Check

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MS How does it affect me

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MS Preperations

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MS Urgency

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MS workload name

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summary for non-techies**

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Direct effects for Operations**

Blocked External Links
Users will be unable to refresh or create new external links to blocked file types, resulting in disrupted workflows and potential data access issues.
   - roles: End Users, Data Analysts
   - references: https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked, https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

Error Messages
Users will encounter #BLOCKED errors when attempting to create new links to blocked file types, leading to confusion and frustration.
   - roles: End Users, Project Managers
   - references: https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked, https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

Loss of Data Refresh
Existing links will display the last successfully refreshed values but will not update, potentially leading to outdated information being used in decision-making.
   - roles: End Users, Business Analysts
   - references: https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked, https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

Increased Support Requests
The change may lead to an increase in support requests from users who are unaware of the new policy and its implications, straining IT resources.
   - roles: IT Support Staff, Help Desk Agents
   - references: https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked, https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

User Communication Needs
There will be a need for proactive communication to users about the upcoming changes to avoid confusion and ensure they are prepared for the transition.
   - roles: IT Administrators, Change Managers
   - references: https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked, https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

Configutation Options**

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Opportunities**

Enhanced Security Protocols for External Links
Implementing the new group policy for external workbook links will significantly enhance security by preventing potentially harmful external links from being refreshed. This will protect sensitive organizational data from being accessed or manipulated through blocked file types.
   - next-steps: Review and configure the group policy settings to ensure that external links to blocked file types are appropriately managed. Communicate the importance of this change to users who may rely on such links.
   - roles: IT Administrators, Compliance Officers, Data Security Managers
   - references: https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked, https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

User Training and Awareness
With the impending changes to external workbook links, there is an opportunity to conduct training sessions for users to understand the implications of these changes and how to adapt their workflows accordingly. This will help minimize disruptions and enhance user experience.
   - next-steps: Develop training materials and schedule sessions to inform users about the new policy, the reasons behind it, and how to manage their workbooks effectively. Provide ongoing support for users who may encounter issues with external links.
   - roles: Training Coordinators, IT Support Staff, Department Managers
   - references: https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

Review and Update of Existing Workbooks
This change presents an opportunity to review existing workbooks that contain external links to blocked file types. By auditing these workbooks, organizations can ensure that critical workflows are not disrupted and can update or replace outdated links as necessary.
   - next-steps: Conduct an audit of all workbooks to identify those that contain external links to blocked file types. Collaborate with users to update or remove these links to maintain workflow continuity.
   - roles: Data Analysts, Project Managers, IT Administrators
   - references: https://learn.microsoft.com/en-us/deployoffice/security/internet-macros-blocked, https://support.microsoft.com/en-us/topic/external-workbook-links-to-blocked-file-types-will-be-disabled-by-default-6dd12903-0592-463d-9e68-0741cf62ee58

Potentional Risks**

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IT Security**

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explanation for non-techies**

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