Starting October 2025, File Block Settings in the Trust Center will apply to external workbook links in Excel. Workbooks that attempt to reference blocked file types will either fail to refresh or display a #BLOCKED error.
This change is designed to reduce potential security risks associated with indirect access to unsupported or high-risk file types.
What to expect:
When refreshing existing links:
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Excel will retain the last successfully refreshed value.
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The Workbook Links pane will show which links failed due to blocking.
When creating new links:
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A #BLOCKED error will appear in the cell.
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Inspecting the error will confirm it's due to a restricted file type.
How to Re-enable Refreshing External Links to Blocked File Types (Not Recommended)
Disabling these protections reduces security and should only be done with caution.
1. Open the Registry editor
To open Registry Editor, click Start, click Run, type regedit, and then click OK.
Caution: Editing the registry incorrectly might severely damage your system. Before you make changes to the registry, we recommend that you back up any valued data on the computer.
2. Back up your registry
Before making any changes to the registry it's always best practice to make a backup of your current registry. Select File > Export and create an export file of your registry. Set the export range to All and give it a name like that makes sense to you such as "Registry backup".
For more information see: How to back up and restore the registry in Windows
3. Navigate to the following key:
HKCU\Software\Microsoft\Office\<version>\Excel\Security\FileBlock\FileBlockExternalLinks
Replace <version> with the version of Office you have:
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16.0 for Office 2016, 2019, or 365
4. Modify the value
Double click to open the file you navigated to: FileBlockExternalLinks and change the Value Data to 0.
How To Review File Block Settings?
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Open Excel > click File > Options
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Go to Trust Center > Trust Center Settings
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Select File Block Settings
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Review which file types are currently blocked
