need not only simple deleting data from "custom clean", but also optionally wipe the data (especially thumbnails folder)
We actually have a feature for this, the Secure Deletion option.
You can find out more here: https://support.piriform.com/hc/en-us/articles/360048321751-Change-CCleaner-for-Windows-settings#h_01ET84P1TWXGF6P4VXK3DQFNM9
It's not enabled by default as it can cause the cleaning to take significantly longer, but it is available to interested users.
Thank you! Missed this option..