--

Unmodified installers for flash 32.0.0.465 (released 8dec2020) can be downloaded from here:

http://web.archive.org/web/20201231144810/https://www.adobe.com/support/flashplayer/debug_downloads.html

<Warning> .465 is the final version of flash and has Adobe's kill switch.
<However> The standalone Flash Player projector (flashplayer_32_sa.exe) does not have the kill switch. Only the plugins.

--

Unmodified installers for flash 32.0.0.371 (released 12may2020) can be downloaded from here:

http://web.archive.org/web/20200605082328/https://www.adobe.com/support/flashplayer/debug_downloads.html

<Note> .371 is the last version of the plugins without Adobe's kill switch.

--

You can either install and use .371 or you can install .465 and replace Adobe's files with the fixed files (which defuses the "time bomb" Adobe put in place).
If you decide to just use .371 of the plugin you can still grab .465 of the projector since it doesn't have a kill switch.
Version .371 lasted until 9jun2020. There were 7 releases of flash after .371 so if you use .371 you will be 7 patches behind the final .465 release.

--

Example: You want to fix the NPAPI plugin.

1. Close your browser
2. Go to C:\Windows\System32\Macromed\Flash
3. Rename "NPSWF64_32_0_0_???.dll" to "NPSWF64_32_0_0_???.dll.original"
4. Copy mms.cfg and "System32 NPSWF64_32_0_0_465--fixed.dll" to C:\Windows\System32\Macromed\Flash
5. Rename the fixed dll into "NPSWF64_32_0_0_???.dll"

6. Go to C:\Windows\SysWOW64\Macromed\Flash
7. Rename "NPSWF32_32_0_0_???.dll" to "NPSWF32_32_0_0_???.dll.original"
8. Copy mms.cfg and "SysWOW64 NPSWF32_32_0_0_465--fixed.dll" to C:\Windows\SysWOW64\Macromed\Flash
9. Rename the fixed dll into "NPSWF32_32_0_0_???.dll"

What the questionmarks are depends on the version of flash you had installed (465 or 371 for example).
Note: If you keep the original DLLs but don't change the extension from .dll Firefox may still use them.
So if it appears to not work make sure you've changed the extension of the original DLLs (or move/delete them).

Step 3 and 7 probably will require you to take ownership of the file before renaming it:
A) Right-click the file and select Properties.
B) On the Security tab, press Advanced.
C) If the "Owner" isn't you, click "Change".
D) Type your account name into the text area and press the Check Names button.
E) After becoming the owner, if there are any "Deny" types in the list of permission entries, select each one and Remove them.
F) Press OK to close the Advanced Security Settings dialog and OK again to close the file's Properties window.
G) Check if you are now able to rename the file.
H) If you still can't rename it, return to the list of permission entries and Add a new one with your account as the "Principal" and make sure it has "Full Control".
I) If you still can't rename it perhaps the file is in use? Try rebooting and then rename it the first thing you do.

--

To avoid some confusion I'll mention that C:\Windows\System32 is where 64-bit files are stored and C:\Windows\SysWOW64 is where 32-bit files are stored.
Let's take the file "System32 Flash64_32_0_0_465--fixed.ocx" as an example, "Flash64" means it is 64-bit and "System32" means it should be stored in the 64-bit part of Windows.
The "System32" folder name comes from Microsoft simply trying to be more backwards-compatible and the confusing "SysWOW64" folder name means "System Windows (32-bit) On Windows 64-bit".
32-bit programs running on 64-bit Windows are automatically redirected by the OS to files in the SysWOW64 folder when trying to access stuff in the System32 folder.

--

The mms.cfg settings file contains options that tells the flash installation to not try and update itself.
If you want to you can add "EnableInsecureActiveXNavigateToURL=1" to allow navigateToURL() in the ActiveX version of the flash plugin. It's used to open websites in many old swf files.
For more mms.cfg options you can check out page 38 of the Adobe Flash Player 32.0 Administration Guide (PDF):
http://web.archive.org/web/20210119042139/https://www.adobe.com/content/dam/acom/en/devnet/flashplayer/articles/flash_player_admin_guide/pdf/latest/flash_player_32_0_admin_guide.pdf
Note that C:\Windows\SysWOW64\Macromed\Flash\mms.cfg seems to be the preferred file to be read by the plugins but the Administration Guide says to also put a copy in C:\Windows\System32\Macromed\Flash\mms.cfg so do that just to be on the safe side.
In order for Google Chrome to find mms.cfg it needs to be in the following location (maybe need to replace "Default" with "Profile <number>", also maybe need to create folders):
C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\Default\Pepper Data\Shock-wave Flash\System\mms.cfg

Note that the standalone Flash Projector exe does not read the mms.cfg settings file.
The projector's settings can be handled by "Flash Player Settings Manager", located at "C:\Windows\SysWOW64\FlashPlayerApp.exe", next to an applet control panel file (.cpl).
SysWOW64\FlashPlayerApp.exe SHA-256: 4174B02AE28540B185848C973B25454652ECECB6B22A63E2907EF39FEE3ED5B5 (842296 bytes = 822 KiB)
SysWOW64\FlashPlayerCPLApp.cpl SHA-256: 355B50CA47E13E9C778DD9A95AB186ACFB4A6F2E5B9F4B8C774D1798D17DE775 (175160 bytes = 171 KiB)
This program appears as "Flash Player (32-bit)" on Window's Control Panel ("Control Panel\All Control Panel Items").
It can also be accessed by right-clicking a flash opened in the projector and selecting "Global Settings..." from the context menu.
On the Advanced tab in the Flash Player Settings Manager there's a button to manage Trusted Location Settings where you can set a single swf or whole folder as trusted on your computer.
If a swf is "trusted" the projector will allow it to open links or connect to the Internet.
The "trustedPaths" are stored inside a Local Shared Object ("flash cookie") located here:
C:\Users\%USERNAME%\AppData\Roaming\Macromedia\Flash Player\macromedia.com\support\flashplayer\sys\settings.sol
These global settings (meaning the projector's settings) could also be managed by visiting Adobe's online "Global Security Settings panel" at:
https://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager04.html

It should also be mentioned that even if you disregard the "global settings" the projector exe is not truly a standalone way to play flash files.
Certain flashes depends on .swz "cache files" in order to function, stored in subfolders here:
C:\Users\%USERNAME%\AppData\Roaming\Adobe\Flash Player\AssetCache\
These "cache files" could be embedded into the swf file or they could be referenced via "Default Linkage", which reduced the size of the final swf but requires the projector (or flash plugins) to download the .swz file from Adobe if your computer don't already have it.
So if Adobe ever removes the ability to download missing .swz files from their servers the flashes that depend on them will stop working. Unless manually downloaded from somewhere and put into the right place, of course.
A common use case of .swz was when TLF text fields were used in the flash files. The "Text Layout Framework" allowed you to get more control over how the text looked, TLF was later dropped by Adobe.
At the time of writing it is unclear (to me) how difficult it will be to restore 100% functionality to the projector if used on a future copy of Windows 10 that was not shipped with anything flash-related.
Hopefully installing the NPAPI plugin will take care of setting up everything the projector EXE needs as well.

--

The ActiveX version of the flash plugin is named "Flash.ocx" on Windows 10. It is used by programs such as Media Player Classic or Internet Explorer to play swf files.
Adobe's ActiveX installer (flashplayer_32_ax_debug.exe) will insist on Windows Update handling the ActiveX installation on Win 10. Microsoft will most likely no longer provide this service.
If you don't have the ActiveX version of flash on Win 10 any more it should be possible to find a guide to "hack" it back manually, without installation.

--

All fixed files are only 6 bytes different from the original.
These bytes:          "00 00 40 46 3E 6F 77 42"   (1610409600000.0 stored as a little-endian double, it is milliseconds from the Unix Epoch, which translates to "2021 Jan 12 00:00:00 UTC")
Were replaced with:   "00 00 00 00 00 00 F8 7F"   (NaN stored as a little-endian double, it is "not a number", which makes Adobe's "time bomb" always evaluate to false when checked against the current time)

Below are file sizes and SHA-256 hashes of the non-official fixed/defused files (and mms.cfg).

System32 Flash64_32_0_0_465--fixed.ocx
28335160 bytes (27 MiB)
3687AD0BE95678A4C43F9F2DD71AB88DC550F633FB2A6444AA9C6A74273FBB00

System32 NPSWF64_32_0_0_465--fixed.dll
27914808 bytes (26 MiB)
2CD75FD6C6ABE0EBA4FC1914007BB965D729F6E988973036EBC5223AA9A1F2E1

System32 pepflashplayer64_32_0_0_465--fixed.dll
32965176 bytes (31 MiB)
AEA8E2CB4EBCD84E6F59C6C207790293E02DCA2DD094D47A5B83C64F4D68A704

SysWOW64 Flash32_32_0_0_465--fixed.ocx
21339704 bytes (20 MiB)
AE0A263C120ABB02046AA125910C556F560926A7BA931F24D4700421741D3132

SysWOW64 NPSWF32_32_0_0_465--fixed.dll
21235768 bytes (20 MiB)
61BD18A5C3F2755C57C46CA16E9935777CD55DA9789C98E3C6897EA09713E865

SysWOW64 pepflashplayer32_32_0_0_465--fixed.dll
19014200 bytes (18 MiB)
0A88A11834EB3D08524B87DE433CEB22F961A5574D82F90F9C87EC93651F7BA5

mms.cfg
97 bytes
39B41C052071B73E1A16B62EF3DEE338792E6AC700FEF10DEAD7C1319EF4C0D9

linux_32-bit_NPAPI_libflashplayer--fixed.so
16066652 bytes (15 MiB)
7B244843593CD77AE78679FDBAED83B0141CB95C2D7886C047E592C1581BA20E

linux_64-bit_NPAPI_libflashplayer--fixed.so
17804712 bytes (16 MiB)
100849108B472CBED2EBDE6F1B54FDEDE67D6A0880FEE5F28F0E3E751F811D4F

linux_PPAPI_64-bit_libpepflashplayer--fixed.so
20717600 bytes (19 MiB)
3666A6C350F411A80359A1E0897134F4BF482930BEF83598BBF90A1A91F366DA

--

Below are SHA-256 hashes and file sizes (in bytes) of Adobe's official files.
These can be obtained through the two WaybackMachine URLs at the top of this text file.
The last 9 hashes are the plugins that Adobe's final installer contains, these are the files you then replace with the fixed versions.

03177DA0FE1C83F71BC748BFACA0E8291A240D9095344055D858019CA4A4454C  :     81920  :  32.0.0.371 Extra = Macromedia Flash Local Content Updater for Linux = local_content_updater-linux.tgz
2DDC0F8C1D67F43BC112931D7E840BC3DDA34DEF9DEE7C2BDF62A3AB4D9761BB  :    153600  :  32.0.0.371 Extra = Macromedia Flash Local Content Updater for Macintosh = local_content_updater-osx.tgz
1206E748CD2803E80E760B4580E0CA9C48FDB560155A795826BB23488F23905C  :     66390  :  32.0.0.371 Extra = Macromedia Flash Local Content Updater for Windows = local_content_updater-windows.zip
2DBDB9AF55DEF3AF239D1AA3E7AF89606BAD097506E3F5C8EEFB5510B3F66E3F  :     51200  :  32.0.0.371 Extra = Macromedia Flash Local Content Updater source for Macintosh-Unix = local_content_updater-src.tgz
BA7F800E97642FBD4193AB5E6C259C6C541E51BCBCAFCA5766760456CFC4597A  :     15357  :  32.0.0.371 Extra = Macromedia Flash Local Content Updater source for Windows = local_content_updater-src.zip
66927DB00B2AED2EC2159961C2381277C67153E8A26B763AB328C94FAB64DA85  :    472345  :  32.0.0.371 Extra = playerglobal.swc to target the latest version APIs = playerglobal32_0.swc
C60EA4359D38AB1DAEEDF14CC5C4F28D0D1026911518B3985A4D59F593D5F631  :   8863404  :  32.0.0.371 Linux = Flash Player Plugin content debugger (32-bit) - NPAPI = flash_player_npapi_linux_debug.i386.tar.gz
4D7E580B91E3E014B7F9977584162D2AB95D2E47799510A5531326CA3A3B34FF  :   9428984  :  32.0.0.371 Linux = Flash Player Plugin content debugger (64-bit) - NPAPI = flash_player_npapi_linux_debug.x86_64.tar.gz
B261766CB49E101B9605A3740F26C9121EBA40770AF8AD036C130706E1FF1D9B  :   9935871  :  32.0.0.371 Linux = Flash Player Plugin content debugger (64-bit) - PPAPI = flash_player_ppapi_linux_debug.x86_64.tar.gz
0AE5BC767E966F4C4EB1E69BFC8589A4473AC272099F463029DF2EE86C4E94A2  :   8513930  :  32.0.0.371 Linux = Flash Player Projector (64-bit) = flash_player_sa_linux.x86_64.tar.gz
F6F1C364887FB7FB03A1CEC5AF26305348AB29B20165FB7CCB58C916BC986B58  :   8829187  :  32.0.0.371 Linux = Flash Player Projector content debugger (64-bit) = flash_player_sa_linux_debug.x86_64.tar.gz
73614E8F2493E8E5835EC1A2FE2E3E21C73C4355EC0382C470C64079086EFFA2  :  13710677  :  32.0.0.371 Macintosh = Flash player content debugger for Firefox, Safari - NPAPI = flashplayer_32_plugin_debug.dmg
AD95995EDEB53C48658C3AC02DD5E73B644C200AE30B0C611FA991209DB63761  :  21089182  :  32.0.0.371 Macintosh = Flash Player content debugger for Opera and Chromium based applications - PPAPI = flashplayer_32_ppapi_debug.dmg
BEB33AE0BCCA5BA50248C8553A957BD87AE54E1BC3E63A8B0747AE5B4F04A030  :   9625120  :  32.0.0.371 Macintosh = Flash Player projector = flashplayer_32_sa.dmg
3B1B06FC7D9DE321DF239799954A65B712235015CEBFE2CE53E49FAC373617D0  :   9953143  :  32.0.0.371 Macintosh = Flash Player projector content debugger = flashplayer_32_sa_debug.dmg
9D26875DB8646FDD368C9BB79347C7897E3C3F1467D1F8D7496371F1729DFE5D  :  21077048  :  32.0.0.371 Windows = Flash Player content debugger for Firefox - NPAPI = flashplayer_32_plugin_debug.exe
AEBE2DE364CE81C5728BAEE879D6D6A87024D589C0DFDF837BF6151583B5BE24  :  21133880  :  32.0.0.371 Windows = Flash Player content debugger for Internet Explorer - ActiveX = flashplayer_32_ax_debug.exe
020DC5FED0AC093949A37CEF594DB4CD08B539BBC914DEDC97301525118ED69C  :  21568056  :  32.0.0.371 Windows = Flash Player content debugger for Opera and Chromium based applications - PPAPI = flashplayer_32_ppapi_debug.exe
E4C5BF84926AF3C888753E27185AA9A0D5227EDE7B366A3C3C75AB595D94F3F0  :  15453752  :  32.0.0.371 Windows = Flash Player projector = flashplayer_32_sa.exe
97E20347A8E3DC98F7F8CCBA91B831BF6419F83A012F267BD23504C0572A680D  :  16281656  :  32.0.0.371 Windows = Flash Player projector content debugger = flashplayer_32_sa_debug.exe

03177DA0FE1C83F71BC748BFACA0E8291A240D9095344055D858019CA4A4454C  :     81920  :  32.0.0.465 Extra = Macromedia Flash Local Content Updater for Linux = local_content_updater-linux.tgz
2DDC0F8C1D67F43BC112931D7E840BC3DDA34DEF9DEE7C2BDF62A3AB4D9761BB  :    153600  :  32.0.0.465 Extra = Macromedia Flash Local Content Updater for Macintosh = local_content_updater-osx.tgz
1206E748CD2803E80E760B4580E0CA9C48FDB560155A795826BB23488F23905C  :     66390  :  32.0.0.465 Extra = Macromedia Flash Local Content Updater for Windows = local_content_updater-windows.zip
2DBDB9AF55DEF3AF239D1AA3E7AF89606BAD097506E3F5C8EEFB5510B3F66E3F  :     51200  :  32.0.0.465 Extra = Macromedia Flash Local Content Updater source for Macintosh-Unix = local_content_updater-src.tgz
BA7F800E97642FBD4193AB5E6C259C6C541E51BCBCAFCA5766760456CFC4597A  :     15357  :  32.0.0.465 Extra = Macromedia Flash Local Content Updater source for Windows = local_content_updater-src.zip
7D4D6168D27603CFB3B750302448E354E0BBC1BDD58F5D101C3DCF6891E9BB65  :    472260  :  32.0.0.465 Extra = playerglobal.swc to target the latest version APIs = playerglobal32_0.swc
BCA9126035B69BA74ED69A5CB5EF5A6BC8FBD0290E31F6FC662E5DAD85A47AAB  :   8863902  :  32.0.0.465 Linux = Flash Player Plugin content debugger (32-bit) - NPAPI = flash_player_npapi_linux_debug.i386.tar.gz
7E4C598349E271634B3B190540AC70D7E0F20E7D161CD5359D611E4FD807E712  :   9429939  :  32.0.0.465 Linux = Flash Player Plugin content debugger (64-bit) - NPAPI = flash_player_npapi_linux_debug.x86_64.tar.gz
63348ACD3F3B8F18B89C5ABCE41A057211B2D08C476A924835B719F2830435D5  :  10202321  :  32.0.0.465 Linux = Flash Player Plugin content debugger (64-bit) - PPAPI = flash_player_ppapi_linux_debug.x86_64.tar.gz
883F7AA23301FC80DE879501157533A4ACDBFEE0721ED7C57676DC032FDF96C3  :   8514041  :  32.0.0.465 Linux = Flash Player Projector (64-bit) = flash_player_sa_linux.x86_64.tar.gz
1ADBD1F2DF130C6F6A5E9D4DA1E23513E6C682EEEC0C9153BF17BCBECA1F4AC6  :   8829953  :  32.0.0.465 Linux = Flash Player Projector content debugger (64-bit) = flash_player_sa_linux_debug.x86_64.tar.gz
D91EBAEED0C11058AC91F4555C65D2CD39A202522882AD6DD94907E27244A03C  :  14611756  :  32.0.0.465 Macintosh = Flash player content debugger for Firefox, Safari - NPAPI = flashplayer_32_plugin_debug.dmg
722036A7C9A90F03A32CF481673870A5C435BF89642B7D81F778654BF4BB810F  :  13982649  :  32.0.0.465 Macintosh = Flash Player content debugger for Opera and Chromium based applications - PPAPI = flashplayer_32_ppapi_debug.dmg
236ECEF54A7D6C3EED739C74B7E14946B07B6156CBCEDDA3BBBF444F1D17023A  :   9902593  :  32.0.0.465 Macintosh = Flash Player projector = flashplayer_32_sa.dmg
7A9A043E1481768D58ED9DE8FF8644AA95D73EA7A0F5BA59B77FD4E71F7C25FD  :  10169829  :  32.0.0.465 Macintosh = Flash Player projector content debugger = flashplayer_32_sa_debug.dmg
687F951DB45F4C2547F8759528F25D0ED9C9A918421D8A73D157AC0A61E01369  :  21387320  :  32.0.0.465 Windows = Flash Player content debugger for Firefox - NPAPI = flashplayer_32_plugin_debug.exe
719DE5C7EE5DEF94416B7868AA51CC773F1D48A84C43290DC896FC5C24F8DAA2  :  21453368  :  32.0.0.465 Windows = Flash Player content debugger for Internet Explorer - ActiveX = flashplayer_32_ax_debug.exe
9CDBBC7D1BB45B25491893221C742B6B71A14185319D88C2703A232486D481D3  :  22157368  :  32.0.0.465 Windows = Flash Player content debugger for Opera and Chromium based applications - PPAPI = flashplayer_32_ppapi_debug.exe
A4B333AC1DA12026989549015303D82231982838BCCFB544BA5FD188746066F0  :  15983672  :  32.0.0.465 Windows = Flash Player projector = flashplayer_32_sa.exe
9D51DF0C26E9EC4717A3DA2E184CDE831CA139D49E4A7C2F9E26028F8C4DFA52  :  16811576  :  32.0.0.465 Windows = Flash Player projector content debugger = flashplayer_32_sa_debug.exe

7EE800C040EE0FF84FE71AA84DAAFCBA53FDCBBFD2FE3538601E261C0C84501A  :  16066652  :  (unmodified 32.0.0.465 plugin) linux_32-bit_NPAPI_libflashplayer.so
9945DA1E47A4326417BE3AC5CBD7E4074839EB88367C43FE0CEF18355D3E6778  :  17804712  :  (unmodified 32.0.0.465 plugin) linux_64-bit_NPAPI_libflashplayer.so
993103E8A506F3C85CBBC98352E6E2CE6798AFDB9DFB28C4789FBC26E42BF14D  :  20717600  :  (unmodified 32.0.0.465 plugin) linux_PPAPI_64-bit_libpepflashplayer.so
6C3B6A419167929BFAE3572F709258E044B39AEB55B45B597760CB51ADE784AB  :  28335160  :  (unmodified 32.0.0.465 plugin) System32 Flash64_32_0_0_465.ocx
93D082C5F012BE2D7CDAFFDA642B45597BE952F647EADBA88EEB23D11AD79E50  :  27914808  :  (unmodified 32.0.0.465 plugin) System32 NPSWF64_32_0_0_465.dll
39D8BFEE52AF530F723C24FAF1EA07C05943153B56A90F62AC1C0F305F49105E  :  32965176  :  (unmodified 32.0.0.465 plugin) System32 pepflashplayer64_32_0_0_465.dll
603BF12B05CF4025CBA18E058E90CC3CF61DB1FEC0A2B456DB6975A5EDC0F40D  :  21339704  :  (unmodified 32.0.0.465 plugin) SysWOW64 Flash32_32_0_0_465.ocx
EA61128DDDC701977CF75183F927DF6C8A5BB68F088C80545C0ACE8B803C542E  :  21235768  :  (unmodified 32.0.0.465 plugin) SysWOW64 NPSWF32_32_0_0_465.dll
384062D195D300BD00B360571BB116C2C274C9718947238E8A143D2FA5D9236F  :  19014200  :  (unmodified 32.0.0.465 plugin) SysWOW64 pepflashplayer32_32_0_0_465.dll

--

Sometimes Windows Update didn't update Flash.ocx to Adobe's final version.
Just for good measure here are two alternative hashes of an unmodded version of Flash.ocx that has been found on the system after 1jan2021 even though Windows Update was running throughout December2020.

64-bit version (in System32): A3A9A644EDEA647E00BFAA93ABB9F383F540448009B9FAC3242C655DA2500D0D (28979096 bytes = 27 MiB)
32-bit version (in SysWOW64): F6108F3D0CEFAF3518788214BC090DBEB0E68BC6C13A978B7E40742D7E018A40 (22874520 bytes = 21 MiB)

--