Microsoft Boosts Windows Security by Disabling File Previews for Downloads

Microsoft has enhanced Windows security by disabling the preview pane for downloaded files in File Explorer, effective from October 14, 2025. This update addresses a vulnerability that allowed attackers to exploit HTML elements in files to harvest NTLM hashes and sensitive credentials. The new feature automatically applies the 'Mark of the Web' attribute to files from untrusted sources, preventing previews and displaying a warning message. Users can still preview trusted files by unblocking them in properties.

This proactive measure aims to reduce the attack surface in environments using legacy authentication protocols, balancing security with user experience.