OMG this thumbnail folder is a GOLDMINE of screenshots of searches, what I copy pasted......ya not cool.
that's brutal!
From the looks of it, they are not securely deleted when they do is unknown too.
Also Ccleaner does not clean then by default either.
ok I did browser.pagethumbnails.capturing_disabled;true and it is still bulding the screenshots thumbnails after restart.
browser.newtab.url;about:blank
browser.newtabpage.enabled;false
browser.newtabpage.storageVersion;1
browser.pagethumbnails.capturing_disabled;true
browser.pagethumbnails.storage_version;2