Microsoft has never been a fan of “registry cleaner” CCleaner, and now it has just given Microsoft another reason to keep it on the blacklist of built-in security software. The latest CCleaner public release was found to remove the synchronized Firefox extension settings and other data.
When you sync two computers with Firefox, the place where Firefox 79 stores extended data has changed and the data is stored in the Profile directory. Unfortunately, CCleaner deletes the contents of the Profile directory, which means that browser extension data and settings are constantly deleted, so that every time you use the clean-up software, you need to reconfigure Firefox’s extension settings.
The issue was reported to Piriform when Firefox was still in beta in July, but the company took no action and many users’ data is now being lost with the automatic upgrade of Firefox 79.
The solution is, of course, to uninstall CCleaner, but if for some reason you still want to continue using it, you can remove the relevant files (Storage-sync-v2-sqlite-shm and Storage-sync-v2.sqlite-wal) from the daily cleanup by going to CCleaner and Options and Add and Add File.