Hi kendall_63, Thank you for your suggestion. I might also suggest to mention this in user feedback.You may submit feedback directly to the Advocacy team through the following page:

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The User Advocacy team reviews all feedback and reports on the findings to the product teams and relevant parties, helping to influence and shape our products.

There shouldn't be any new data in the disk cache from the Private Browsing mode session. What plugins and extensions possibly store is something different. Note that the disk cache isn't cleared when you enter PB mode, so data that was present in the cache will still be there and is used once you close all PB mode windows and tabs.

See also the about:cache page.

Thanks for your responses. I was just surprised to see the files in cache2 and "doomed" folder that could be recovered. Also, I see small entries of web visits in files that are resident in MFT entries that have already been deleted. Those are now stuck there, clearly visible with any recovery program. Like I said before, If you "truly" want to remove any tracks of visits, (less ISP records) do not let FF delete your cache or cookies. Use SDelete or Eraser to wipe them. They will also wipe or zero-out data in files resident in the MFT.

Did you ever do a search in the Windows registry to see what other programs store there, especially MS programs like Internet Explorer?

Windows is not very secure when it comes to deleting data and only sets a delete flag in the MFT and doesn't even clear the index entry with the complete cluster chain and other meta data like happens in FAT16 and FAT32, so even fragmented files can easily be restored successfully if clusters haven't been reused.