[tbb-bugs] #30171 [Applications/Tor Browser]: Always accepting third party cookies seems to break first party isolation

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#30171: Always accepting third party cookies seems to break first party isolation
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 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:  closed
 Priority:  High                                 |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:  fixed
 Keywords:  TorBrowserTeam201904R, tbb-          |  Actual Points:
  linkability                                    |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Changes (by gk):

 * status:  new => closed
 * keywords:  TorBrowserTeam201904, tbb-linkability =>
     TorBrowserTeam201904R, tbb-linkability
 * resolution:   => fixed


Comment:

 Replying to [comment:2 acat]:
 > I think this is coming from the pref observer in torbutton.js.
 >
 > It keeps in sync several prefs, amongst them
 `network.cookie.cookieBehavior` and `privacy.firstparty.isolate`. In this
 case, changing the `network.cookie.cookieBehaviour` via UI is indirectly
 flipping `privacy.firstparty.isolate`. And if the latter is false then
 `firstPartyDomain` is not populated and circuit display will always show
 `--unknown--`, the catch-all circuit.
 >
 > Is this pref syncing still logic necessary? If that's not the case, here
 is a patch which just removes this dependency between those two prefs,
 which should solve this issue:
 https://github.com/acatarineu/torbutton/commit/30171

 Ugh. Thanks for the patch and, yes, we should get rid of that footgun.
 Merged to `master` (commit 053c98697a4b00171a31e86399137ecb6f47ddfc).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30171#comment:5>
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