It doesn't wipe data Rated 2 out of 5 stars
I tested on several portable FF versions (old and new, and without ANY add-ons except for SS and Ask For Sanitize), with several SS versions (old and new), and I ALWAYS could restore, with a simple file recovery program ("Restoration"), after the alleged "wiping" took place, the fully intact images I had downloaded for testing purposes.
I seem to remember that formerly SOME (not all) files were no more usable after a wiping operation. The file recovery program formerly still displayed the file names (in the FF cache format), their size and date, but the content of the files had been replaced with question marks when I opened them in a text editor, so most likely some real wiping had taken place. Not sure why I can't reproduce that anymore. I've removed SS for now. But I'll try any future versions.
BTW, the bug I mentioned with regard to SS's wiping choice no more appearing in the "Clear History" dialog is related to the "Biscuit" add-on (manages permanent cookies). After disabling that add-on, the options reappeared.
Two stars (one is for your effort to keep dealing with the problem). ;-)
As you noticed SS wipes only the content of cache files:
+) file names in cache format (i.e. AB345GF, etc.) don't hold sensitive information;
+) modified date/time is changed to the date/time of the wiping operation;
+) file size is kept unchanged, but I can plan to change it also to reduce the risk to be detected.
Anyway, it is still a mystery to me the reason why I'm not able to reproduce the behavior you reported :(
For sure something goes wrong during wiping operation and it quits suddenly. After that FF complete the operation deleting cache files from filesystem (ok, this is expected).
Did you noticed errors in the Error Console of FF ?
PS: I'm planning a new version of SS with a better (more secure) use of pseudo-random numbers. But this not relevant for your issue.
Thanks a lot for your tests