KB5078766: improves the reliability of choosing trusted catalog files

March 10, 2026—KB5078766 (OS Build 20348.4893)

Improvements
This security update contains fixes and quality improvements from KB5075906 (released February 10, 2026) and KB5082314​​​​​​​ (released March 2, 2026). The following summary outlines key issues addressed by this update. Also, included are available new features. The bold text within the brackets indicates the item or area of the change.

• [Secure Boot] With this update, Windows quality updates include additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. This targeting is based primarily on client device diagnostic data; due to limited data, servers are unlikely to qualify, though not explicitly excluded. Devices receive new certificates only after demonstrating sufficient successful update signals, maintaining a controlled and phased rollout.
• [Windows System Image Manager​​​​​​​] Improved: This update improves the reliability of choosing trusted catalog files. It adds a warning dialog that helps you confirm that the file you select comes from a trusted source.

If you've already installed previous updates, your device will download and install only the new updates included in this package.