[tor-bugs] #28368 [Applications/Tor Browser]: determine if media.decoder.recycle.enabled allows any linkability

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#28368: determine if media.decoder.recycle.enabled allows any linkability
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     Reporter:  mcs                  |      Owner:  tbb-team
         Type:  defect               |     Status:  new
     Priority:  Medium               |  Milestone:
    Component:  Applications/Tor     |    Version:
  Browser                            |   Keywords:  tbb-
     Severity:  Normal               |  linkability,ff60-esr,tbb-mobile
Actual Points:                       |  Parent ID:
       Points:                       |   Reviewer:
      Sponsor:                       |
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 In Fennec, `media.decoder.recycle.enabled` is set to `true` (see
 mobile/android/app/mobile.js; although the comment there implies that this
 is only enabled on nightly builds, the definition is not enclosed in an
 #ifdef).

 It is unclear exactly what this preference does, but it seems to cause
 media decoders to be reused for decoding new audio or video elements. If
 detectable state is left inside a decoder and if reuse occurs across
 sites, this could mean there is a linkability risk. We should investigate.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28368>
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