Hello,
I am having an issue with the combination CCleaner (CC) and Firefox (FF), both on the latest release (V5.72, 81.0)
Within FF i have deleted several search engines like Bing and DuckDuckGo and within CC i have disabled their extensions using 'Tools','Bowser plugins'.
After restarting FF and starting CC, the search engines don't show in FF but do show re-enabled in CC.