Preparing Windows for Adobe Flash End of Life on December 31, 2020

On December 31, 2020, Adobe finally ended support for the Flash Player. From this point on, Flash has reached the end of its lifecycle (end-of-life, EOL), new versions or updates will no longer be released. In this article, we’ll explain what a Windows administrator needs to know about the end of support for Flash Player.

Since 2017, Adobe has been advising all developers to migrate their existing Flash projects to HTML5, WebGL, and WebAssembly open formats. The transition period ends later this year, and on December 31, Adobe will remove the Flash Player download page from its site.

To check if Flash Player is installed on your computer/browser, go to the check page https://helpx.adobe.com/flash-player.html

KB4577586: Update for the Removing Adobe Flash Player on Windows

In October 2020, Microsoft released KB4577586 to remove embedded Adobe Flash from supported Windows versions (Windows 8/8.1/10 and Windows Server 2012/2012R2/2016/2019).

• The KB4577586 update only removes the Adobe Flash Player built into Windows 10 (and other current Windows versions). If you manually download and install Flash Player from Adobe site or another source, it won’t be removed;
• You cannot uninstall update KB4577586 after installation. This means that you can no longer install Adobe Flash Player on your Windows device (in order to use Flash again, you will have to rollback to a restore point, reset or reinstall your Windows).

Update KB4577586 (Update for Removal of Adobe Flash Player) is currently only available for manual download from Microsoft’s Update Catalog.

To install the update, just run the downloaded file windows10.0-kb4577586-x64.msu.

If you try to uninstall the Update for Removal of Adobe Flash Player that disables Flash support on Windows 10, you will receive an error:

wusa.exe /uninstall /kb:4577586

Windows Update Standalone Installer
Update for Removal of Adobe Flash Player is required by your computer and cannot be uninstalled.

Uninstall Adobe Flash Player in Older version of Windows

In order to uninstall Flash Player in legacy Windows versions (Windows 7/XP and Windows Server 2008R2/ 2003), in which Flash is not built into the OS image, you need to use a special Uninstaller from Adobe. You can download it here https://fpdownload.macromedia.com/get/flashplayer/current/support/uninstall_flash_player.exe.

Close browsers and other applications that might be using Flash and run the downloaded file uninstall_flash_player.exe

It remains to manually delete all the remaining Flash files from the following folders:

C:\Windows\system32\Macromed\Flash
C:\Windows\SysWOW64\Macromed\Flash
%appdata%\Adobe\Flash Player
%appdata%\Macromedia\Flash Player

Disable Flash Player in Windows via WSUS

Update KB4577586 is currently optional in Windows Update and WSUS. Most likely in early 2021 Microsoft will make it recommended or even mandatory.

The KB4577586 update can be manually imported into WSUS

If the Failed error appears when importing an update, you must enable TLS 1.2 strong encryption support for .Net Framework 4 version on the WSUS server. To do this, create the DWORD (32-bit) parameter named SchUseStrongCrypto and value 1 under the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319. To apply the new settings, you need to restart your computer.

After importing the update to WSUS, you can approve it for installation on the target group of computers/servers (target groups can be created manually in WSUS console or configured via GPO) .

How to Use Adobe Flash Player After 12 Jan 2021?

At the end of December 2020, Adobe officially ended support for Falsh Player. From January 12, 2021, Flash Player forcibly blocks the playback of any swf content in all browsers and displays the following message:

Adobe Flash Player is out of date.

When you try to update the plugin, or click on the picture in the Flash Player window, you will be redirected to the Adobe page with the Flash End of life description.

Due to the high volume of requests from corporate customers, there is a small workaround that allows you to temporarily enable Flash content to play on specific sites.

Create a text file mms.cfg with the following configuration:

EnableAllowList=1
AllowListRootMovieOnly=1
AllowListUrlPattern=https://vca.woshub.com:443
AllowListUrlPattern = *://site1.woshub.com/AllowListUrlPattern = https://*.woshub.com/
SilentAutoUpdateEnable=0
AutoUpdateDisable=1
EOLUninstallDisable=1

You need to specify in the AllowListUrlPattern parameter the URLs of all websites for which you want to temporarily allow playing Flash content.

The mms.cfg file must be copied to domain computers using Group Policiy, logon scripts, SCCM, etc. The table below shows the paths where you need to copy the mms.cfg file, depending on the browser and Windows version:

Then in the browser on a web page with Flash content, select Adobe Flash -> Allow, refresh the page, click on Flash content and in the bottom caption “Adobe Flash Player was blocked because it is out of date” select “Run this time”.

This is a temporary workaround, because in the summer of 2021, Microsoft will release a cumulative update for all supported versions of Windows that will completely remove the built-in Flash Player.