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This security update resolves a Microsoft SharePoint spoofing vulnerability. To learn more about the vulnerability, see Microsoft Common Vulnerabilities and Exposures CVE-2021-24104.

Note: To apply this security update, you must have the release version of Microsoft SharePoint Server 2019 installed on the computer.

Improvements and fixes

This update removes the Document and List Static Data Fixed SampleJob timer job from SharePoint Server. This timer job is intended for SharePoint Online use only. Therefore, it should not be included in SharePoint Server.

Note: To fix this issue, you have to install KB 4493230 together with this update.

This security update also contains fixes for the following nonsecurity issues in SharePoint Server 2019. To fix these issues, you have to install KB 4493230 together with this update.

  • Fixes an issue in which all the subsites themes will be changed at the same time when a root site theme is changed.

  • Fixes an issue in which some texts in the Chinese (Traditional) language version of SharePoint Server 2019 appear as the Chinese (Simplified) language in modern UI.

  • Fixes an issue in which Try link is shown as a link in the New link pane if the Address field is empty in high contrast mode.

  • Fixes an issue in which the focus is not clear on the back button in the Create Site pane.

  • Fixes an issue in which there is no close button to close the Create a site dialog box by using the keyboard.

  • Fixes an issue in which the Rich Text toolbar disappears when you input many lines of text.

  • Fixes an issue in which DatePicker doesn't render in the modern item properties pane in document libraries.

  • Fixes an issue in which a list folder can't be renamed successfully in the modern UI.

  • Fixes an issue in which a folder in a modern view document can't be opened after you install the ListView Command Set extension.

  • Fixes an issue in which in a modern view custom list, the preview of a lookup item doesn't work from the details pane and the preview is truncated in the list view.

  • Fixes an issue in which the left navigation pane disappears when you create a sub link and then delete it.

  • Fixes an issue in which link items are missing when you edit the left navigation pane.

  • Fixes an issue in which the Change the look Panel doesn't have a close button.

  • Fixes an issue in which the focus is not visible in the site Activity tile.

  • Fixes an issue in which the focus status is missing when you select the More Option button in the communication site left pane and then select an option item on the popup menu.

  • Fixes an issue in which the focus status is missing when you select the Following or Not Following button.

  • Fixes an issue in which Narrator doesn't announce anything about the More Option button in the site's left pane.

  • Fixes an issue in which the required aria attributes are missing in the Create List panel.

  • Fixes an issue in which Narrator does not announce the number of items and the order number of each item in Featured Links.

  • Fixes an issue in which the Get the mobile app button doesn't have sufficient color contrast.

Known issue in this update


After you install this update, you can no longer delete list item attachments in the item detail panel.


Microsoft is investigating this issue and will post more information in this article when a fix becomes available.


To work around this issue, see KB 5003294.

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: March 9, 2021 (KB5001208).

Security update replacement information

This security update replaces previously released security update 4493161.

File hash information

File name

SHA1 hash

SHA256 hash




File information

Download the list of files that are included in security update 4493231.

Information about protection and security

Protect yourself online: Windows Security support

Learn how we guard against cyber threats: Microsoft Security

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