June 12, 2018—KB4284874 (OS Build 15063.1155)

This update includes quality improvements. No new operating system features are being introduced in this update. Key changes include:

• Provides support to control usage of Indirect Branch Prediction Barrier (IBPB) on some AMD processors (CPUs) for mitigating CVE-2017-5715, Spectre Variant 2 when switching from user context to kernel context. (See AMD Architecture Guidelines for Indirect Branch Control and AMD Security Updates for more details). For Windows client (IT pro) guidance, follow the instructions in KB4073119. Use this guidance document to enable IBPB on some AMD processors (CPUs) for mitigating Spectre Variant 2 when switching from user context to kernel context.
• Provides protections from an additional subclass of speculative execution side channel vulnerability known as Speculative Store Bypass (CVE-2018-3639). These protections aren't enabled by default. For Windows client (IT pro) guidance, follow the instructions in KB4073119. Use this guidance document to enable mitigations for Speculative Store Bypass (CVE-2018-3639) in addition to the mitigations that have already been released for Spectre Variant 2 (CVE-2017-5715) and Meltdown (CVE-2017-5754).
• Addresses a mobile-only issue where enterprise files could be saved as personal files even though the Windows Information Protection policy is enabled on the device.

• Addresses an issue where firmware updates cause devices to go into BitLocker recovery mode when BitLocker is enabled, but Secure Boot is disabled or not present. This update prevents firmware installation on devices in this state. Administrators can install firmware updates by:

  1. Temporarily suspending BitLocker.
  2. Immediately installing firmware updates before the next OS startup.
  3. Immediately restarting the device so that BitLocker doesn’t remain in the suspended state.
• Addresses an issue where booting with Unified Write Filter (UWF) turned on may lead to stop error 0xE1 in embedded devices, particularly when using a USB hub.
• Increased the Internet Explorer cookie limit from 50 to better align with industry standards.
• Addresses a binary serialization compatibility issue for the CultureAwareComparer class.
• Security updates to Internet Explorer, Microsoft Edge, Microsoft scripting engine, Windows Desktop Bridge, Windows apps, Windows Server, Windows wireless networking, Windows storage and filesystems, Windows app platform and frameworks, and Windows virtualization and kernel.

If you installed earlier updates, only the new fixes in this package will be downloaded and installed on your device.

For more information about the resolved security vulnerabilities, see the Security Update Guide.

Microsoft is not currently aware of any issues with this update.

This update will be downloaded and installed automatically from Windows Update. To get the standalone package for this update, go to the Microsoft Update Catalog website.

File information

For a list of the files that are provided in this update, download the file information for cumulative update 4284874.