***NOW UPDATED with Apple MacOS instructions, in addition to Microsoft Windows*** 

***Also updated with the solution to the mms.cfg file not working due to the UTF-8 bug***

You may have seen plenty of announcements over the past few years about Adobe Flash coming to the end of life. Various browser manufacturers announced they will disable Flash. Microsoft announced they will uninstall Flash from Windows using a Windows Update (although only the Flash that came automatically with Windows, NOT user-installed Flash). Apple completely disabled Flash in Safari. Below is the dreaded Flash End of Life logo that you will see once Flash is finally turned off:

Yes, I agree with Steve Jobs — Flash is buggy and not secure. However, there are many IT manufacturers out there that used Flash to build their management software interfaces. Some common examples are VMware vSphere, Horizon, and HPE CommandView. That management software is not going away, even though most of it is older. In fact, some of these Flash-managed devices will be there for the next 10 years. So, what can the desperate IT administrator do to manage his or her devices?

Adobe sends users for extended Flash support to a company called Harman. HPE charges money for older CommandView support. Do not pay any money to these companies to use Flash.

Preparation

I am not recommending Chrome or Edge browsers for the below solution because they will auto-update and newer versions will not support Flash at all. Further, turning off auto-update in Chrome and Edge is difficult.

Here are 3 methods to get Flash running on your favorite website. Windows methods assume 64-bit Operating systems. If you want to try 32-bit Windows, the files are available, but the functionality has not been tested (although it will probably work). All the files talked about in these methods are downloadable below:

firefox-flash-end-solution-versions.zip_.pdf — Right click on the link and choose “Save Link As” or “Download Linked File As”. Save the file to your computer. Unhide file extensions. Remove _.pdf from the end of the name and Unzip/ExtractAll the file.

The file contains:

policies.json
Firefox Setup 78.6.0esr-64bit.exe
Firefox Setup 78.6.0esr-32bit.exe
Firefox 78.6.0esr.dmg

flash-eol-versions.zip_-1.pdf — Right click on the link and choose “Save Link As” or “Download Linked File As”. Save the file to your computer. Unhide file extensions. Remove _-1.pdf from the end of the name and Unzip/ExtractAll the file.

The file contains:

mms.cfg
Flash player for Firefox and Win7 – use this for Solution: install_flash_player.exe
Flash for Safari and Firefox – Mac: install_flash_player_osx.dmg
Flash for Opera and Chromium – Mac: install_flash_player_osx_ppapi.dmg
Flash Player for Chromium and Opera browsers: install_flash_player_ppapi.exe
Flash Player for IE active x: install_flash_player_ax.exe
Flash Player Beta 32 bit – May 14-2020: flashplayer_32_sa.exe flashplayer_32_sa.dmg
flash_player_32_0_admin_guide.pdf

Method 1 — Microsoft Windows, if you have Internet Explorer browser and Flash already installed

This method applies to many older Windows Operating systems like Server 2008, 2012, 2016 and Windows 7 and even older Windows 10. It assumes a 64-bit operating system.

1. Do NOT upgrade Internet Explorer to the Microsoft Edge browser.
2. Set Internet Explorer to be the default browser in Default Programs.
3. Download the mms.cfg file.
4. Open the mms.cfg file with Notepad.
5. Edit the URL on the right of the Equals sign with an address of the Flash website or file that you need.
   1. Ex. AllowListUrlPattern=https://localhost/admin/
6. If you need additional websites, place them on the next lines, like in this example.
   1. AllowListUrlPattern=https://localhost/admin/
   2. AllowListUrlPattern=http://testwebsite.com/
   3. AllowListUrlPattern=*://*.finallystopflash.com/

7. Save mms.cfg file on the desktop.
   1. Important: if you did not use my file, but you are creating the file yourself, makes sure in Notepad Save As dialog, you select “All Files” as the type, and “UTF-8” as the Encoding.
8. Copy the mms.cfg file into the following directory: C:\Windows\SysWOW64\Macromed\Flash\
   1. That disables Flash updates and allows to use Flash on specified websites.
   2. If you don’t see this directory, it means Flash is not installed and you need to use Method 2 instead.
9. Restart the Internet Explorer browser.
10. Go to your website.
11. This will open Internet Explorer with Flash functional.

Method 2 — Microsoft Windows, if you don’t have Internet Explorer and/or Flash installed

This method applies to almost any Windows machine. It assumes a 64-bit operating system.

1. If you already have another version of Firefox installed, uninstall it.
2. Download the “Firefox Setup 78.6.0esr-64bit.exe” and “policies.json” files. This Firefox installer is the Enterprise version (what you need).
3. Install Firefox ESR, but do NOT open it, or if it opens, close right away.
4. In the “C:\Program Files\Mozilla Firefox\” directory, create a folder called “distribution”
5. Put “policies.json” file into the folder “distribution” — this disables automatic Firefox updates.
6. Start Firefox ESR.
7. Go to URL: about:policies
8. Check that “DisableAppUpdate” policy is there and it says “True”.
9. Set Firefox to be the default browser in Default Programs.
10. Download “Flash player for Firefox and Win7 – use this for Solution: install_flash_player.exe” and “mms.cfg”.
11. Double click on the install_flash_player.exe to install Flash for Firefox. Click all Next prompts.
    1. If you are prompted to choose “Update Flash Player Preferences”, select “Never Check for Updates”.
12. Open mms.cfg file with Notepad
13. Edit the URL on the right of the Equals sign with an address of the Flash website or file that you need.
    1. Ex. AllowListUrlPattern=https://localhost/admin/
14. If you need additional websites, place them on the next lines, like in these examples:
    1. AllowListUrlPattern=https://localhost/admin/
    2. AllowListUrlPattern=http://testwebsite.com/
    3. AllowListUrlPattern=*://*.finallystopflash.com/
15. Save mms.cfg file on the desktop.
    1. Important: if you did not use my file, but you are creating the file yourself, makes sure in Notepad Save As dialog, you select “All Files” as the type, and “UTF-8” as the Encoding.
16. Copy the “mms.cfg” file into the following directory: C:\Windows\SysWOW64\Macromed\Flash\
    1. That disables Flash updates and allows to use Flash on specified websites.
17. Restart Firefox ESR.
18. When going to the flash website you specified, click on the big logo in the middle, then “Allow”.

Method 3 — Apple MacOS

This method applies to almost any MacOS version.

1. If you already have another version of Firefox installed, uninstall it.
2. Download “Firefox 78.6.0esr.dmg” and “policies.json” files. This Firefox ESR for Mac installer is the Enterprise version (what you need).
3. Open the DMG file. Drag the Firefox ESR icon to the Applications folder, which installs it on the Mac. Do NOT open Firefox ESR yet.
4. Open the Terminal application.
5. Type the following and press Enter (start typing from xattr).
   1. xattr -r -d com.apple.quarantine /Applications/Firefox.app
      1. This allows Firefox customization without corrupting the application.

6. Go to the Applications folder. 
7. Right click on the Firefox.app application and select “Show Package Contents”.
8. Go to Contents>Resources folder and when there create a folder called “distribution”.
9. Put “policies.json” file into the folder “distribution” — this disables automatic Firefox updates.

10. Start Firefox ESR.
11. Go to URL: about:policies
12. Check that “DisableAppUpdate” policy is there and it says “True”.
13. Download “Flash for Safari and Firefox – Mac: install_flash_player_osx.dmg” and “mms.cfg”.
14. Double click on the install_flash_player_osx.dmg to mount the disk. Double click the installer to install Flash for Firefox. 
15. When asked to choose on “Update Flash Player Preferences”, select “Never Check for Updates (not recommended)”.

15. Place the mms.cfg file on the Desktop. Open mms.cfg file with TextEdit.
16. Edit the URL on the right of the Equals sign with an address of the Flash website or file that you need.
    1. Ex. AllowListUrlPattern=https://localhost/admin/
17. If you need additional websites, place them on the next lines, like in these examples:
    1. AllowListUrlPattern=https://localhost/admin/
    2. AllowListUrlPattern=http://testwebsite.com/
    3. AllowListUrlPattern=*://*.finallystopflash.com/

18. Save mms.cfg file to the Desktop. Copy the mms.cfg file.
19. Paste the “mms.cfg” file into the following directory:
    1. /Library/Application Support/Macromedia/     (Mac Hard Drive>Library>Application Support>Macromedia)
20. If there is already an existing mms.cfg file in there, Replace it.
    1. That disables Flash updates and allows to use Flash on specified websites.

21. Restart Firefox ESR for Mac. 
22. When going to the flash website you specified, click on the big logo in the middle, then “Allow”.

References

https://support.mozilla.org/en-US/questions/1283061

https://community.adobe.com/t5/flash-player/adobe-flash-availability-after-2020/td-p/10929047?page=1

https://support.mozilla.org/en-US/kb/deploying-firefox-customizations-macos