[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:  new
 Priority:  High                                 |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  TorBrowserTeam201904, tbb-           |  Actual Points:
  linkability                                    |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by 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

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30171#comment:2>
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