My Firefox settings are such that cookies should be deleted when Firefox is closed, except for a few exceptions. But I've noticed that CCleaner finds some cookies (Options > Cookies) that shouldn't be there (while Firefox is closed) and that are not in the exceptions (of both Firefox and CCleaner). Firefox doesn't find these cookies (Options > Privacy > Show cookies). These cookies all seem to be from websites I access with Firefox.
I've cleaned with CCleaner but they reappear. I didn't select the Intelligent Cookie Scan.
My Flash Player settings are such that no website can store data on my PC.
CCleaner detects and lists them for Firefox Portable I'm using when cleaning:
Cleaner > Applications > Firefox > Cookies
I had wondered why all of a sudden some cookies were being created for Adblock Plus subscriptions I have that never were previously, now I know they're putting super cookies into that SiteSecurityServiceState.txt file.
The solution is to delete SiteSecurityServiceState.txt, create a new one and set it to "read only".
There were also cookies created by Flash Player despite I set it up to not store data on my PC: you also need to set up an online panel on the Macromedia website.
From what I understood the fact that Firefox can't delete super cookies is a bug that still have to be fixed, but I'm not sure about that...
I made a winapp2.ini entry to clean it for Firefox Portable. Maybe read-only works on it, I don't know but I'd imagine it would either get stored elsewhere or in memory. The only sites I've seen in it are from Adblock Plus subscriptions. I also don't use or have Flash installed anymore, had no need for it anymore starting several months ago.
Here's that winapp2.ini entry I made:
[Firefox Portable Super Cookies*]
LangSecRef=3026
DetectFile=%SystemDrive%\PortableApps\FirefoxPortable\Data\profile\SiteSecurityServiceState.txt
Default=False
FileKey1=%SystemDrive%\PortableApps\FirefoxPortable\Data\profile|SiteSecurityServiceState.txt