
After the October 2025 or a later Windows security update is installed, File Explorer preview pane will display the following 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.
Note: This change of behavior applies to files marked with MotW after download from the internet, and to files viewed on an Internet Zone file share.
If you are confident in the safety of both the file and its source, you may remove the internet security block.
To remove the block for a downloaded file, right-click the file in File Explorer, select Properties, and then select Unblock.
Note: The change might not take effect immediately but will be effective after the next login.
To remove the block for files on an Internet Zone file share, use the Internet Options control panel’s Security tab to add the file share’s address to either the Local intranet or Trusted sites security zone.
Warning: This configuration change will relax the security posture for all files from the listed file share.