This security update resolves a spoofing vulnerability that exists when Office Online does not validate origin in cross-origin communications handlers correctly. To learn more about the vulnerability, see the following security advisories:
Note To apply this security update, you must have the release version of Microsoft 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:
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.
Security update deployment information
For deployment information about this update, see security update deployment information: November 12, 2019.
Security update replacement information
This security update replaces previously released security update 4475595.
File hash information
How to get help and support for this security update
Help for installing updates: Protect yourself online
Help for protecting your Windows-based computer from viruses and malware: Microsoft Security
Local support according to your country: International Support