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Do not save any cookies in Private Browsing

Firefox Tracking protection
Yaron replied 9 years ago
Yaron
Yaron

Hello,

Firefox does save some cookies in Private Browsing (e.g. Mozilla, Facebook). Those cookies are not displayed in FF Cookies window but tools like CCleaner show them.

How can I prevent FF from saving them?

Thank you.

Hello, Firefox does save some cookies in Private Browsing (e.g. Mozilla, Facebook). Those cookies are not displayed in FF Cookies window but tools like CCleaner show them. How can I prevent FF from saving them? Thank you.

All Replies (6)

FredMcD
FredMcD

Where are you finding these cookies?

In Private Browsing, all session data is stored in a special file. When Firefox is closed, that file is removed.

Yaron
Yaron Question owner

Hello FredMcD,

Thanks for replying. I appreciate it.

You can see these super cookies if you install CCleaner. Options -> Cookies.

If you check for add-ons updates, you get a cookie from Mozilla. And there are many others.

Best regards.

Modified by Yaron

cor-el
cor-el
  • Moderator

Do these cookies show if you type/paste document.cookie in the Web Console or in the Storage Inspector if you revisit these websites?

Firefox might be accessing some services (e.g. DOM push) that you have granted access. Some special cookies with appid unequal to 0 also won't show in the Cookie Manager. It is always best to avoid using external cleaners to avoid your personal data getting corrupted.

Yaron
Yaron Question owner

Hello cor-el,

Thanks for replying. I appreciate it.

Searching a bit more, I've found a solution:

Firefox does save some cookies in Private Browsing. They're stored in SiteSecurityServiceState.txt in your profile.

Setting that file to "Read Only" would prevent FF from storing them.

I wonder if there's a more elegant solution.

Best regards.

cor-el
cor-el
  • Moderator

It is not cookies that are stored in the SiteSecurityServiceState.tx file, but that file stores HSTS and other site specific settings. If you set this file to read-only then HSTS won't be working properly and you may be vulnerable to MITM attacks when you open a HTTP link.

If your cleanup software inspects this file then you should exclude it (or better exclude your entire profile folder).

Yaron
Yaron Question owner

Hello again cor-el,

Thank you for the additional info.

If I remember correctly, some of the data stored in that file is "Super Cookies". CCleaner and other tools regard them as such.

Anyway, the issue is clearer now. :) I appreciate your help.

Best regards.