apt – How can I keep Firefox and Thunderbird automatically being updated to the newest version?

I received notice from my IT department to update Firefox and Thunderbird due to security issues. I thought it would be as easy as going clicking something like “Search for updates” in the menu, but I couldn’t find such an option. I ran sudo apt update and then sudo apt upgrade because I think that is how all installed software is usually updated.

However, these are the version numbers of my Firefox and Thunderbird installations as listed in the settings:

firefox version

thunderbird version

Though if I download Firefox directly here, I get version 88 at the time of writing this. Thunderbird’s newest version is 78.10. What’s going on?