I try to take my security and privacy at least somewhat seriously when online and use a few addons to help with that. I have the followingaddons currently installed.
Adblock Plus 2.2.1
Cookie Exporter 1.5
Cookie Importer 1.1
Cookie Monster 1.1.0
Element Hiding Helper for Adblock Plus 1.2.3
TinEye Reverse Image Search 1.1
In Firefox I have cookies disabled. Running Firefox with none of the above addons installed or not installed still allows Firefox to block cookies.
I frequently check my cookie permissions using CCleaner and the only cookies that appear are those that come in when I run Internet Explorer (which is rare). I add cookies to my "Cookies to keep" list in CCleaner as necessary. I also add cookies to Firefox on an as needed basis (for example avast.com so I can log in and post questions such as this).
Recently I installed the Avast! WebRep addon when I installed the free version of Avast!. When the addon is disabled in Firefox the cookie permissions behave as expected. When I have the addon enabled I receive cookies from all websites that I go to.
Disable the WebRep addon if it is installed. Steps to reproduce this issue:
1) I am running Windows 7 64bit SP1 with all patches installed.
2) Install the latest version of Firefox.
3) Configure Firefox to block all cookies. You can find how to perform that configuration here:http://support.mozilla.org/en-US/kb/block-websites-storing-site-preferences
4) Install CCleaner.
5) Run CCleaner to make sure all cookies are deleted.
6) Run Firefox. Go to any website that you do not have cookies stored for.
7) Close Firefox.
Run CCleaner. You should see no cookies to delete. Run CCleaner anyway.
9) Install the Avast WebRep addon (or enable it if it was disabled).
10) Start Firefox.
11) Go to the same website you went to or another one if you feel like it.
12) Close Firefox.
13) Run CCleaner. You will now see cookies for the domain that you went to. You should not see third party cookies. Clean out the cookies.
14) Disable WebRep and test again and see if any unwanted cookies reappear.
If you know what you are doing you can also revert Firefox back to it's original configuration by following the instructions in the following link:http://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-most-problems
You may want to go into the following locations to back things up just in case something breaks for you:
Please advise what I need to configure in Firefox to keep Avast! WebRep from adding cookies. I can disable WebRep and my cookie issue goes away.
Thank you for your time and attention in this matter.