Microsoft is facing a significant security challenge due to hundreds of millions of unsupported PCs still in use, particularly those running Windows 10. Nearly a billion users have not transitioned to Windows 11, with about 500 million on PCs that cannot upgrade. Microsoft has released its final Patch Tuesday updates for 2025, addressing 56 vulnerabilities, including three zero-days. Windows 10 users not enrolled in the extended security updates (ESU) program will no longer receive automatic updates, with November’s Patch Tuesday marking the first serious fixes not extended to them. Users can enroll in the ESU program at no cost, allowing access to recent updates, with no deadline for enrollment until October 2026. Delaying enrollment increases vulnerability to attacks.