[Firefox "Default zoom" Custom Setting Getting Cleared]

I was able to do some more testing as well, and it seems to be the "content-prefs.sqlite" file that affects the setting (tested in Firefox version 103).

When running CCleaner with the "Firefox" "Site Preferences" option checked, it resets the "browser.content.full-zoom" property that's in the "content-prefs.sqlite" file. After, if I manually restore a backup that I previously made of the "content-prefs.sqlite" file, it restores the Firefox global "default zoom" custom setting that I had previously set.

[Firefox "Default zoom" Custom Setting Getting Cleared]

The global "Default zoom" setting in Firefox gets cleared when running Cleaner with the "Firefox" "Site Preferences" option checked.

To replicate, first change the global setting in Firefox here: Tools > Settings > General > Zoom > Default zoom

Replicated in Firefox version 103