DanCaro

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.

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