hi, can you launch firefox with the -jsconsole argument and look in the network tab of the browser console if you find more information about that connection there (like the exact url - this might give more information about what is happening)... https://developer.mozilla.org/docs/Tools/Browser_Console

The exact server being contacted is server-54-230-219-14.mrs50.r.cloudfront.net Thank you for your hint about the browser console! After looking there, I found that the connection corresponds to a connection to https://self-repair.mozilla.org/de/repair/ . Now, I see that this corresponds to "Firefox Heartbeat". I didn't know it existed and it isn't listed on the help page that lists automatic connections. I never received a prompt for a rating from Firefox. I don't understand why this makes a connection at every Firefox startup.

thank you for bringing this up - looks like we have to update that page in the knowledge base. in order to disable heartbeat, enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named browser.selfsupport.url. double-click it and change its value to a blank string. https://wiki.mozilla.org/Advocacy/heartbeat