Send telemetry by default
Firefox sends telemetry data by default, it behaves like the most famous windows operating system in its default setting. Mozilla can control the browser remotely via the telemetry, which came recently into action as Mozilla switched on TLS 1.0 and 1.1 off remotely because a group of users that possibly could not view corona information sites correctly. Mozilla did not shout about the normandy feature from the rooftops possibly not to upset its user base. Gentoo's Bugzilla – Bug 713782.
To disable this technology set in global firefox configuration about:config app.normandy.enabled to false.
To find out more about normandy and it features, check the Godzilla Wiki - Firefox/Shield.
Block .onion by default
Tor support is disabled by default. In its default setting users will not be able to access .onion sites using Firefox. This has been also described here: Protonmail's support site for firefox
To enable access to .onion sites set in the global firefox configuration about:config network.dns.blockDotOnion to false.
Disable IRC support channel
After a long evaluation period, Mozilla has switched to Matrix from IRC as its preferred open discussion platform. Mozilla sees Matrix as improvement in usability, accessibility and safety for the Mozilla community, therefore it has disabled its IRC servers for good.
Matrix describes itself as an open, lightweight protocol for decentralized, real-time communications.
Challenge: Try to find only one RFC describing the matrix protocol. Here is a URL to RFC searching engine making your search a no-brainer. If you find something, please let me know. Let me guess, everything works with HTTPS?
Remove the obsolete and unsafe FTP protocol
FTP is unsafe by design, but there is also FTPS. Works the same as BGP and TCP-MD5 hashing. Wait, did not someone yell recently BGP is unsafe and complex on top of it? Yes, it is unsafe by design. Honestly, this does not make a big difference if FTP is supported or not. One security flaw less to care.
Proceed with Caution
If Changing advanced configuration preferences can impact Firefox performance or security. Highly suggestive notification before changing any internals of firefox.
Postmortem
Mozilla foundation turned into Godzilla Foundation, while its famous browser Firefox mutated into unusable piece of shit, zombie crap load. A reason to stop using ZombieVixen. ZombieVixen itself is a data blackhole in its default setting.
There are numerous other arguments not to use the new Godzilla Foundation's ZombieVixen Browser. Find your own. Frankly, disabling predefined defaults in a application feels like back to 1995...
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