CCleaner Bug?

What is this?! Since I downloaded the free version 3.23.1823 64bit every time I try to wipe the free space on C: drive this folder shows up with a bunch of replicating "Z's" after it and it increasingly eats up my drive available space the closer the cleaner gets to completing the "wipe" function! Any one, PLEASE :(

Your space will be restored upon completion. Do not abort.

Thank you kroozer, I will try that!