On the client machine running flash, create a mms.cfg with notepad with content below.
EOLUninstallDisable=1
AutoUpdateDisable=1
EnableAllowList=1
AllowListURLPattern=https://10.224.0.20:8443/
AllowListURLPattern=https://10.218.0.23/
where you enter the website that you want to allow flash to run after "AllowListURLPattern=". If you have multiple sites to use flash, you can add entry.
If you use IE and Firefox, copy mms.cfg to the folder below.
mms.cfg added to path below for Windows Flash
(Windows 32bit) C:\Windows\System32\Macromed\Flash
(Windows 64bit) C:\Windows\SysWOW64\Macromed\Flash
I don't use Chrome and Edge. However, you can try to move mms.cfg to the location below.
For Chrome
%localappdata%\Google\Chrome\User Data\Default\Pepper Data\Shockwave Flash\System\mms.cfg
For Edge
%localappdata%\Microsoft\Edge\User Data\Default\Pepper Data\Shockwave Flash\System\mms.cfg
Besides, make sure you don't have apply Microsoft patch KB4577586. Once it is applied, it will uninstall Flash and prevent Flash from installed again.
Below are the instructions to install and uninstall flash in Windows server 2016.
Uninstall Flash in Windows 2016
DISM /Online /Remove-Package /PackagePath:"C:\Windows\servicing\Packages\Adobe-Flash-For-Windows-Package~31bf3856ad364e35~amd64~~10.0.14393.0.mum"
Install Flash in Windows 2016
dism /online /add-package /packagepath:"C:\Windows\servicing\Packages\Adobe-Flash-For-Windows-Package~31bf3856ad364e35~amd64~~10.0.14393.0.mum"
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Finally, got approval to upgrade AppSync to 4.1, and it was upgraded successfully. I don't need to worry about Flash any more.
