@herowoac
Since
r3dfox can't be made
VMP-compliant (
Verified-Media-Path, aka
Widevine security level 2 (L2)), whether you patch
redfox in memory under
Win<8 or patch the actual
widevinecdm.dll itself will have the same net effect: the prominent encrypted services that mandate
VMP won't "work"

in
r3dfox,
period; these include Netflix, AmazonPrimeVideo, CBS.com, Paramount+, Disney+, Spotify, Tidal and most of the commercial/paid for ones... The same is true for
r3dfox+Widevine on
Win8+, where the CDM is natively supported...
If your goal is to use such services under
Win7, then
FxESR-115.xx.x will be (quasi) the only solution until it expires next October; this is because
Mozilla can afford to pay
Google 
a hefty price (in the order of several USD1,000s) to have Firefox's "firefox.exe", "plugin-container.exe" and "xul.dll" files VMP-signed...
If, OTOH, your goal is to make "plain"

encrypted services work, i.e. the ones that only require
Widevine security level 3 (L3), then you can just HexEdit/patch the actual
widevinecdm.dll file; the file's digital signature will become invalidated, sure, but this is only relevant in the context of L2,
not L3...
My legacy OS is
Windows Vista SP2 32-bit with all MS updates till EoS, plus several important WS2008SP2 updates manually installed; browser used is r3dfox-136.0.4.win32.portable; I have been successful in restoring EME/Widevine support in the browser by manually adding a group of
about:config prefs, which then resulted in r3dfox downloading Widevine-v
4.10.2891.0 inside my
r3dfox portable profile; I then "borrowed" the "solution" and some extra wrapper DLL files from the
Supermium project; the Sm "solutions" took care of the missing API calls (there are 4 under Vista SP2, 2 under Win7 SP1), so the WV CDM can be now properly loaded when called by the browser:
Of course, things would've been more straightforward if
K4sum1 had agreed to compile the browser with the " --enable-eme=widevine,playready" buildconfig option (one wouldn't have to manually add the required prefs), however I'm still heavily indebted to him

for his browser offering

; yes, no sandbox for me here still, but, alas, c'est la vie

...
Kindest regards

.