Possible Issue with CCleaner "not wiping free space"?

Hello, i had read a complaint here: http://www.techspot.com/vb/topic129560.html that CCleaner might not be adequately wiping free space or that the data is somehow recoverable. Is this the case with others at all?

It interests me also what the differences are between CCleaner's free space wiper function etc and other free space wiping programs. Any experts who could direct me to good reading or perhaps other forum posts would also be greatly appreciated.

Many thanks for the help.

If you read all the thread in the link the poster states that he was actually looking at data in the MFT, and at that time I don't think that CC had the Wipe MFT option.

There's lots of threads here about wiping free space, and lots of posts saying that it's a waste of time. It's up to you whether you run it.

how do I undo the process? I didn't mean to. I thought it was something else.