I was hoping mozilla would have their users' back, but a default install of Firefox also makes multiple connections to mozilla, google and other domains when started. Some extensions (notably NoScript and Ghostery) ping the mothership.
Safari connects to configuration.apple.com and the google website blacklist. uBlock for Safari tries to update itself even if no one asked it to.
Later edit: I have been told that I am perhaps being unfair to Mozilla. Let's see - I started reading https://support.mozilla.org/en-US/kb/how-stop-firefox-making..., to see how I can stop Firefox from connecting to servers without being requested to. While it's nice that they provide this page, this article's breadth only serves to prove that this browser is out of control when it comes to making connections to servers by itself.
I have the following settings:
* disabled Firefox health report
* disabled crash reporting
* never check for updates
* do not check for addon updates
* block reported attack sites
* block reported forgeries
After reading the page, it turns out that I also have to disable the following from about:config:
* the addons blocklist
* link prefetching
* DNS prefetching
* speculative pre-connections
* firefox Hello
* tiles, even if they were already disabled from the UI
* the default search engine geo-location
* the what's new page
* add-on metadata updating
* the heartbeat
For reference, here are the connections that Firefox tries to establish immediately after startup:
Outgoing to self-repair.mozilla.org (54.230.200.16), Port https (443), Protocol TCP (6), 0 B sent, 0 B received
Outgoing to shavar.prod.mozaws.net (52.26.89.67), Port https (443), Protocol TCP (6), 0 B sent, 0 B received
Outgoing to safebrowsing.google.com (2a00:1450:4001:809::1005), Port https (443), Protocol TCP (6), 0 B sent, 0 B received
Outgoing to tiles.r53-2.services.mozilla.com (52.25.98.110), Port https (443), Protocol TCP (6), 0 B sent, 0 B received
Outgoing to cmp-cdn.ghostery.com (54.152.180.212), Port https (443), Protocol TCP (6), 0 B sent, 0 B received
Outgoing to search.services.mozilla.com (54.69.18.27), Port https (443), Protocol TCP (6), 0 B sent, 0 B received