I am glad that the public backlash forced them to fix a deliberate BACKDOOR that they had introduced (by design) in the Network Extension Framework that macOS Big Sur now forces all the firewalls to use. (At least, they claim to have removed it). But it is hard to trust them again, and I would prefer to use a firewall that uses its own kernel extension to manage the network than using Apple's API again. (Obviously th…
Why do you call it a deliberate backdoor when the Apple developers (see elsewhere in this thread) have said this was a bug?
Before macOS Big Sur / Catalina, many of these application firewalls - Lulu, Little Snitch, HandsOff, TripMode, RadioSilence etc. - all used their own kernel extensions to effectively monitor and block any processes from connecting to the internet.
Firewalls are system security softwares. And naturally Apple would prefer to oversee and have this in-built in their OS. Apple also wants to discourage kernel extensions on macOS (they have some good reasons - a poorly designed kernel extension can make the OS unstable; but mostly its about feature control with Apple).
So they informed all such firewall app developers that their individual kernel extensions will no longer be allowed, and Apple had instead created an OS API specifically for their use case. (They described the features it would have and invited them to give their feedback). And so all application firewalls were forced to update their apps and use this OS API.
But this API had an undisclosed, in-built list of Apple approved applications that no firewall was allowed to block. Someone created that list. Someone added that list in the system, and coded the API to specifically give them special privileges to bypass any application firewalls.
Bugs are accidental. Backdoors like these are intentional.
(You can however take exception to the usage of "Backdoor" here - perhaps from Apple's perspective it was a good design decision as many of these services go wacko, and sometimes even freeze your system, when they aren't allowed to do what they are coded to, like do some operation over the internet. I've often seen CPU spikes and slowdowns when you block some of these services.)