Well it seems Piriform put a little surprise in version 5.55 of CCleaner. It's an Updater. It tells you if any of your programs need updating and offers to do it for you. Now the catch that they don't tell you is once you click on the link to see what program is out of date, a box opens up... and tells you how much you have to PAY for the Updater Program. And the box won't close until you click on the link to start the payment process. Isn't that a load of crap!? I can't figure out how to close
The message box you are describing has a 'No Thanks' option in the bottom left-hand side, as seen in the screen picture below. This will close the message and cancel the software update. If you are not seeing this option please let me know and provide a screenshot if possible.