Sorry, bit late to the party :)
The underlying reason, why you see that message, was already explained above (Firefox had detected its binaries have changed). Let's deal with that reason then.
I guess you have Firefox installed as a snap package? You can figure it out by running snap list
in the terminal to see if firefox
appears in the list.
If that is the case, what you're dealing here with is an aggressive default behavior of Canonical's Ubuntu snap
package manager: it is automatically updating all your installed snap
packages behind your back without asking any additional confirmation from you or telling you anything about it, in explicit form. Some proofs:
https://snapcraft.io/docs/keeping-snaps-up-to-date
Snaps update automatically, and by default, the snapd daemon checks for updates 4 times a day. Each update check is called a refresh.
https://snapcraft.io/blog/how-to-manage-snap-updates
Snaps come with a built-in automatic update mechanism, whereby snaps are refreshed to a new version whenever there’s a new release in the Snap Store. Typically, the refresh occurs four times a day, and in the vast majority of cases, they will complete seamlessly, without any issues.
To be honest, this is the dumbest move of Cannonical, to have such defaults. People are running away from Microsoft Windows, because of such things, and what do they find in one of the most popular Linux distributions? The same thing.
Nevertheless, there're couple of things you can do:
(my own preference) is to remove Firefox as a snap package and install it as a normal deb package, by adding Mozilla apt repository to your apt configs. By doing that, it will be your own decision, when to apply updates, not the Canonical's one
you can consider to configure a snapd so it won't be acting that aggressively as it does by default. But there's a chance, that with the next OS upgrade Canonical will override your configs back to what they think is right.
I know it might sound like I joke, but still - consider to switch to some other Linux distro, as an option, which are not doing the same thing to its users and not pushing snaps that hard. Fedora, Mint, PopOS, Debian and many others - there're plenty of choices