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Cookie exceptions spontaneously change.

  • 5 replies
  • 2 have this problem
  • 33 views
  • Last reply by cor-el

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On the Privacy tab in Options the check box for Accept cookies from sites is unchecked. I pressed the Exceptions button and added many websites to accept cookies from and clicked Allow for Session on each one. Sometimes I go to a website where I have to sign in with a username and password and the site states that my browser is refusing to accept cookies even though I had added the site to the exception list. When I check the exception list, the status of the exception has changed from Allow for Session to Blocked. I have found several exceptions change on their own from allow to blocked and some even have changed again after I changed them back. What could be causing the exceptions to change and is there some way to make the settings persistent?

On the Privacy tab in Options the check box for Accept cookies from sites is unchecked. I pressed the Exceptions button and added many websites to accept cookies from and clicked Allow for Session on each one. Sometimes I go to a website where I have to sign in with a username and password and the site states that my browser is refusing to accept cookies even though I had added the site to the exception list. When I check the exception list, the status of the exception has changed from Allow for Session to Blocked. I have found several exceptions change on their own from allow to blocked and some even have changed again after I changed them back. What could be causing the exceptions to change and is there some way to make the settings persistent?

Chosen solution

Do you have the network.cookie.blockFutureCookies set to true on the about:config page?


Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

  • Do not click the Reset button on the Safe mode start window or otherwise make changes.
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All Replies (5)

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Chosen Solution

Do you have the network.cookie.blockFutureCookies set to true on the about:config page?


Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

  • Do not click the Reset button on the Safe mode start window or otherwise make changes.
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network.cookie.blockFutureCookies;true

I was not aware of this setting and not sure why it was set to true. Based on the description of the setting, I believe this is probably what is causing the issue. I had been manually deleting cookies from specific sites when I have trouble signing in, and those sites seem to be the ones for which cookies were being blocked. I will try setting that property to false and see if that resolves the problem. If not, I will try safe mode and troubleshooting extensions. Thank you very much for your assistance cor-el.

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You're welcome

Yes, if this pref is set to true then you automatically block cookies from a domain by deleting cookies from it.
So resetting the pref to false should fix this.

If you do not keep the change then check for extension or a possible user.js file that sets this pref.

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I tried toggle on the property and it set to false, and tested the result, and it seemed to solve the problem. The odd thing is that it still said "user set" (on both true and false) so I tried reset then it changed from boolean to string ""; weird. Whatever it is as long as it's not set to boolean true (or even if it's deleted) it appears to have solved the problem I was having. Thank you.

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Yes, this pref is a hidden pref and only appears on the about:config page if you have created it yourself.
A reset of such a pref makes it show as an empty String value and a restart of Firefox will remove such a pref, so what you see is perfectly normal.