Security First: Windows 11 Disables File Previews for Web Downloads

Security First explains that in a Windows 11 cumulative update, Microsoft changed File Explorer to disable previews for files downloaded from the internet. For security reasons, the preview pane will no longer display content from such files, so, for example, clicking an image downloaded from the web won’t generate a preview in the right-hand pane.

The change is intended to patch a flaw that could potentially expose NTLM authentication hashes when processing unsafe files, since a preview of an HTML file with external references could disclose sensitive information. If a user tries to preview one of these files, a warning will be shown: “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.” Users can unblock a downloaded file via Properties to re-enable previews, though the file can still be opened normally. The update applies to all supported editions of Windows 11, Windows 10 (including ESU versions), and Windows Server 2012 through 2025, including 23H2, according to support.microsoft[.]com.