i am glad that some of the others posted about this. i noticed something similar and wanted to post about it. i only use ccleaner’s custom clean. i don’t use ccleaner’s “health check” because it doesn’t show what is going to be removed when you run it.
after i run ccleaner’s custom clean, to remove junk-files, like the OP said, the ccleaner window “shades out.” it goes dark, briefly. afterwards, i proceed to close ccleaner and i don’t notice any ill-effects from it.
i don’t know what strange process ccleaner is doing to cause it to go dark, briefly, after i run its cleaning process.
i don’t see any new ccleaner “startup” entries, or any new ccleaner “tasks.”