[tbb-bugs] #16983 [Tor Browser]: Favicon requests not isolated if one opens the tab list dropdown

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#16983: Favicon requests not isolated if one opens the tab list dropdown
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     Reporter:           |      Owner:  tbb-team
  someone_else           |     Status:  needs_review
         Type:  defect   |  Milestone:
     Priority:  major    |    Version:
    Component:  Tor      |   Keywords:  tbb-linkability,
  Browser                |  TorBrowserTeam201509R
   Resolution:           |  Parent ID:
Actual Points:           |
       Points:           |
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Comment (by arthuredelstein):

 Replying to [comment:14 mcs]:
 > Arthur, thanks for the detailed explanation. Kathy and I understand the
 code now. But we are seeing an assertion failure in the new code inside
 ThirdPartyUtil::GetFirstPartyURIInternal() during browser startup with a
 Mac OS debug build:
 >  Assertion failure: IsElement(), at
 ../../../dist/include/mozilla/dom/Element.h:1369
 > I will attach a stack trace, but the short story is that
 ThirdPartyUtil::GetFirstPartyIsolationURI() is being called from
 nsContentUtils::LoadImage(). The image URI is moz-
 anno:favicon:https://www.torproject.org/images/favicon.ico#-moz-
 resolution=16,16
 >
 > Maybe you need to add an IsElement() call before calling AsElement()?

 Thanks for catching this mistake and for the stack trace. For some reason
 I'm not seeing an assertion failure when I run a debug build on OS X. I
 wonder what I'm doing differently.

 In any case, here's a new version of the patch with an IsElement() check
 added:
 ​https://github.com/arthuredelstein/tor-browser/commit/16983+1

 I tested this on a debug build and it seems to be working properly.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16983#comment:15>
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