Windows 10 Users Get Extended Security Update with Critical Fixes
Microsoft has rolled out an extended security update for Windows 10, KB5099539, which addresses a record-breaking 570 vulnerabilities and includes additional security fixes. The update is particularly important for users who are running Windows 10 Enterprise LTSC or have enrolled in the free Windows 10 Extended Security Updates (ESU) program, as it extends their access to security updates until October 12, 2027.
The KB5099539 update is part of Microsoft’s quarterly Patch Tuesday cycle, which has seen a significant increase in vulnerabilities being addressed. This latest patch includes fixes for two exploited and one publicly disclosed zero-day flaws, making it a critical update for users who want to stay protected against known attacks. The update also brings several bug fixes, including issues with OLE Automation, File Explorer, and the Recycle Bin.
One of the key changes in this update is the addition of support for SHA-2 certificate thumbprints for trusted Remote Desktop (RDP) publishers. This change aims to improve RDP security by reducing phishing risks through better management of .rdp files. However, Microsoft warns that an intentional security hardening change may impact legacy applications that rely on unregistered third-party TDI transports.
To determine whether you are affected by the TDI transport registration requirement, check the Windows System event log in Event Viewer for AFD Event ID 16003 entries. If you find such entries, it means your application is using an unregistered TDI transport, and you may need to take action to resolve the issue.
For users who have enrolled in the ESU program or are running Windows 10 Enterprise LTSC, installing this update is straightforward. Simply go into Settings, click on Windows Update, and manually perform a ‘Check for Updates’ to download and install KB5099539. The update will bring your system up to build 19045.7548 (for regular users) or build 19044.7548 (for Enterprise LTSC 2021).
In summary, the KB5099539 extended security update is an important patch that addresses critical vulnerabilities and includes additional security fixes. If you are running Windows 10 and have not yet installed this update, do so as soon as possible to stay protected against known attacks.
Source: Bleeping Computer — 2026-07-14