[tor-bugs] #26607 [Applications/Tor Browser]: verify that subpixel accuracy of window scroll properties does not add fingerprinting risk

[Tor Bug Tracker & Wiki]

#26607: verify that subpixel accuracy of window scroll properties does not add
fingerprinting risk
-------------------------------------+-------------------------------------
     Reporter:  mcs                  |      Owner:  tbb-team
         Type:  defect               |     Status:  new
     Priority:  Medium               |  Milestone:
    Component:  Applications/Tor     |    Version:
  Browser                            |   Keywords:  tbb-fingerprinting,
     Severity:  Normal               |  ff60-esr, TorBrowserTeam201807
Actual Points:                       |  Parent ID:
       Points:                       |   Reviewer:
      Sponsor:                       |
-------------------------------------+-------------------------------------
 ​As of Firefox 55, the `window.pageYOffset`, `pageXOffset`, `scrollX`, and
 `scrollY` properties now return data with subpixel accuracy. We think this
 means "half pixels on a macOS Retina or other high resolution display." We
 should determine if this adds any fingerprinting risks (and whether the
 values returned are already rounded when `privacy.resistFingerprinting` is
 set to `true`). See:
  https://bugzilla.mozilla.org/show_bug.cgi?id=1151421

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26607>
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