[tbb-bugs] #20915 [Applications/Tor Browser]: Web developer network tab breaks first-party isolation in some cases

[Tor Bug Tracker & Wiki]

#20915: Web developer network tab breaks first-party isolation in some cases
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     Reporter:  gk                   |      Owner:  tbb-team
         Type:  defect               |     Status:  new
     Priority:  Medium               |  Milestone:
    Component:  Applications/Tor     |    Version:
  Browser                            |   Keywords:  ff52-esr, tbb-
     Severity:  Normal               |  linkability
Actual Points:                       |  Parent ID:
       Points:                       |   Reviewer:
      Sponsor:                       |
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 There are rare cases where the first-part isolation breaks if the Web
 developer Network tab is open. This got first reported on our blog:
 https://blog.torproject.org/blog/tor-browser-65a5-released#comment-224102

 Steps to reproduce (works both in the stable and the alpha series on Linux
 at least):

 1) Start a fresh Tor Browser and set the Torbutton log level to "3"
 2) Open the Network tab in the Web developer console (Ctrl + Shift + Q)
 3) Go to https://torproject.org
 4) Reload the page with the arrow in the URL bar

 Result:

 Torbutton INFO: tor SOCKS isolation catchall:
 https://www.torproject.org/images/onion-heart.png via
 --unknown--:de6a28fb71abeba4febbbdde61de345e

 It is actually only the request for the onion heart that is affected. And
 having the Network tab open is crucial for reproducing the bug.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20915>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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