Microsoft says it has blocked another Windows feature due to security concerns.
File preview disabled on File Explorer
Microsoft just made it harder for you to preview files downloaded from the Internet in File Explorer to reveal the NTLM hash. This change mitigates a known vulnerability to prevent the possible theft of sensitive data by malicious people such as passwords, codes and more.
Starting with Windows security updates released on or after October 14, 2025, File Explorer automatically disables the preview feature for files downloaded from the Internet. This change is designed to improve security by preventing a vulnerability that could reveal NTLM hashes when users preview potentially unsafe files. For more details, see the following FAQ about this change.
Therefore starting from the October cumulative update, the function that allows you to view files in the File Explorer preview pane is disabled by default on files downloaded from the web or that are marked with MotW (Mark of the Web) by displaying this message:
The file you are trying to preview may harm your computer. If you trust the file and the source you received it from, open it to view its contents.
In case you were sure of the origin of the file you can disable this preview blocker in File Explorer as explained below.
If you are confident in the security of both the file and its origin, you can remove the Internet security block. To do this, right-click the file in File Explorer, select Property and so Unlock .
What do you think of this choice by Microsoft? Do you use this old protocol? Let us know in the comments.
Article from Windows Blog Italy
Source | Microsoft
