Bottom line: Microsoft's update addresses at least 398 security vulnerabilities, reducing the attack surface for Windows users.
What's happening: Microsoft released updates for Windows 10, Windows Server, and Internet Explorer 11, addressing weaknesses in the Windows Print Driver, Windows PDF Viewer, and Internet Explorer 11. A previously unpatched vulnerability in the Windows Print Driver was being actively exploited by attackers, while two publicly disclosed vulnerabilities in the Windows PDF Viewer and Internet Explorer 11 were also patched today.
What to do: Security teams should review and apply these patches to Windows 10, Windows Server, and Internet Explorer 11 systems, and consider implementing additional security measures to protect against targeted attacks.