CCleaner showed me a pop-up window this morning about saving me storage space if I cleaned. I just clicked OK and didn't pay it much attention. I was surprised to find that my recycle bin had been emptied even though I don't have that box checked in the list of things CCleaner cleans. I don't know if this was a glitch, or if I didn't read the pop-up carefully enough. I'm wondering if others have had this happen. If this has been addressed elsewhere, I will appreciate being pointed in that direction.
Are you sure that it was CCleaner and not Windows Storage Sense? (Or something else you may have installed).
A few questions to see if we can work out what may have happened:
CCleaner Pro or Free?
Did you open and run CCleaner after you got the prompt? If so did you run Health Check or Custom Clean?
What are you Smart Cleaning 'Junk' settings?