[tor-bugs] #9308 [Firefox Patch Issues]: JavaScript's BrowserFeedWriter() leaks installation paths on OS X and Windows

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#9308: JavaScript's BrowserFeedWriter() leaks installation paths on OS X and
Windows
-------------------------------------+-------------------------------------
     Reporter:  cypherpunks          |      Owner:  mikeperry
         Type:  defect               |     Status:  needs_review
     Priority:  critical             |  Milestone:
    Component:  Firefox Patch        |    Version:
  Issues                             |   Keywords:  tbb-fingerprinting,
   Resolution:                       |  tbb-easy, interview,
Actual Points:                       |  GeorgKoppen201404R
       Points:                       |  Parent ID:
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Comment (by gk):

 Replying to [comment:23 arthuredelstein]:
 > I've added a new patch that fixes the original vulnerability reported in
 this ticket (BrowserFeedWriter). Because the patch,
 ​https://hg.mozilla.org/mozilla-central/rev/e9ea1662020a, requires a
 number of previous patches, a full backport would be rather complex. But
 we can get a workable fix simply by imitating the patch's removal of a
 single line. Deleting this line excises the BrowserFeedWriter constructor
 from the global JavaScript "window" API. Without the BrowserFeedWriter
 constructor, the privacy-leaking JS exception is no longer triggerable.

 While this is a smart move it breaks subscribing to feeds via the browser.
 Trying to subscribe to one a user gets
 {{{
 ReferenceError: BrowserFeedWriter is not defined
 }}}
 in her error console and a broken website.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/9308#comment:24>
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