PDF Preview Issue in File Explorer – Windows 11 24H2 and 25H2

Hi Team,

We are using Windows 11 24H2 and 25H2 across our environment and are experiencing an issue with PDF file previews in File Explorer.

Error Message:

"The file you are attempting to preview could harm your computer. If you trust the file and the source you received it from, open it to view its contents."

We have already performed the following troubleshooting steps:

Installed all the latest Windows security updates and patches.

Manually unblocked the PDF files via:

• Right-click file → Properties → General tab → Unblock
  • After unblocking, the PDF preview works correctly.
    • However, this is not a feasible solution as we have a large number of files stored locally and on network shares.
    Used the following PowerShell command to unblock all files in a folder: PowerShell Get-ChildItem "C:\Folder" -Recurse | Unblock-File Show more lines This works temporarily, but whenever a file is replaced or a new file is added to the same location, the issue reoccurs and the command must be run again. Disabled Show preview handlers in preview pane under:

     

    - File Explorer Options → View tab
    
    However, this did not resolve the issue.
    

Modified the following registry setting:

Plain Text

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments

Show more lines

• Value Name: SaveZoneInformation
• Value: 1

Despite this change, the issue persists.

This issue is affecting more than 500 Windows 11 devices across our environment. We would like to know if there is a permanent solution, known issue, Group Policy setting, or Microsoft-recommended fix to prevent PDF files from being flagged and blocked from previewing in File Explorer.