Firefox needs to be close when running Ccleaner

I am already quite pissed off with this error message. I was just trying to run the CCleaner then the message appeared telling me to exit Firefox though actually did not use it.
I can’t point out any particular reason for it aside from eyeing the service started. Can you please give me any suggestion to take it away? How can I not see it anymore?
It’s totally annoying and I don’t want to see it again and again.

CCLEANER
You must close Firefox/Mozilla to allow the Internet Cache to OK
be cleaned.
Otherwise this process will be skipped.
Do not show me this message again
