The contents of "\Users\XXXXXX\AppData\Roaming\Mozilla\Firefox\Profiles\XXXXXXXXX.default\storage" (where XXX is specific to your own profiles) are impossible to autoclear/ autodelete through the given settings, about:config changes, about:preferences changes, or in-browser consoles like CTRL-SHIFT-DEL to clear all history. Deleting all history at exit and checking all inputs still doesn't delete the contents of that particular folder. That folder is now home to indexed databases (idb files) and special supercookies from sites like mega.nz and bostonglobe.com. The latter is particularly worrying as it doesn't seem to load any special html5 application as mega does. Thus, it comes across a perfectly normal site that nonetheless leaves a persistent supercookie. Thus far, I've only been able to successfully detect and delete these cookies and idb files using CCleaner. I've asked this question in a lengthier post which you can find by clicking thru my user profile. Please, any help in automating deletion of these items would be greatly appreciated. To the Firefox devs, please don't let this breach of privacy go unpatched much longer