Piriform released CCleaner 5.70 to address a bug that was causing the app to wipe settings for Firefox extensions installed after upgrading to Firefox 79 when cleaning the web browser’s Internet cache. Bug was caused by a change made by Mozilla in the way Firefox 79 stores extensions’ data within the storage.sync area used to sync data to all devices signed in to the same Firefox Account. The issue was fixed for all Firefox 79 users, but for users who aren’t logged using a Firefox account.
Source: https://www.bleepingcomputer.com/news/software/ccleaner-fixes-bug-that-wipes-firefox-extension-settings/