Description of the security update for Office Online Server: April 14, 2020

Applies to: Office Online Server


This security update resolves a remote code execution vulnerability that exists in Microsoft Word software if it does not correctly handle objects in memory. To learn more about the vulnerability, see Microsoft Common Vulnerabilities and Exposures CVE-2020-0980.

Note To apply this security update, you must have the release version of Office Online Server installed on the computer.

Known issues in this update

  • After you install this security update, Office Online Server logging will be set to Verbose by default. We recommend that you change this setting to Medium by running the following command:

    Set-OfficeWebAppsFarm -LogVerbosity “Medium”

    Note After you run the command, you have to restart the Office Online Service. To do this, run the following command:

    Restart-Service WACSM

Improvements and fixes

This security update contains the following improvement:
  • Improves the file lock management in Word for the web. The file lock is now released more reliably and taken for shorter durations. If the header says Saved when you leave the document, the final save will be faster.

How to get and install the update

Method 1: Microsoft Update

This update is available from Microsoft Update. When you turn on automatic updating, this update will be downloaded and installed automatically. For more information about how to get security updates automatically, see Windows Update: FAQ.

Method 2: Microsoft Update Catalog

To get the standalone package for this update, go to the Microsoft Update Catalog website.

Method 3: Microsoft Download Center

You can get the standalone update package through the Microsoft Download Center. Follow the installation instructions on the download page to install the update.

More information

Security update deployment information

For deployment information about this update, see security update deployment information: April 14, 2020.

Security update replacement information

This security update replaces previously released security update 4484270.

File hash information

File name SHA1 hash SHA256 hash
wacserver2019-kb4484290-fullfile-x64-glb.exe FD98ADEECE16C6F69B5A6325FE3B11333E10E015 F38F53E36A2D7E1E00CC6BA3E3921B7ABD7C4E1B331F0F89E08F886395BCF080

File information

Download the list of files that are included in security update 4484290.

Information about protection and security

Protect yourself online: Windows Security support

Learn how we guard against cyber threats: Microsoft Security