I went back to 5.40 or something when the version that you couldn't change the settings on came out. Since then I've had update unticked and CCleaner blocked in my firewall, but oddly yesterday it suddenly asked for permission through the firewall for the updater - I denied it again of course - but I thought it was odd. I don't use Avast.
It appears there is something a bit untoward going on with CCleaner.