With this release, your screen saver will no longer interrupt WebRTC calls on Firefox, making conference and video calling in Firefox better.
To view your dashboard, type about:protections into the address bar, or select “Protections Dashboard” from the main menu.
Unsupported operating systems do not receive security updates, have known exploits, and can be dangerous to use, which makes it difficult to maintain Firefox on those versions.” As for what is new with today's Firefox 78 release, here is the changelog:
The last security update applicable to macOS 10.11 was made available in July 2018. “While Apple does not have a public policy governing security updates for older macOS releases, their ongoing practice has been to support the most recent three releases.
