[tor-bugs] #20491 [Applications/Tor Browser]: Firefox bug - Bring back Global Private Browsing Mode instead of current fake

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#20491: Firefox bug - Bring back Global Private Browsing Mode instead of current
fake
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     Reporter:  bugzilla                  |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  Medium                    |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Major                     |   Keywords:
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
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 Currently TBB uses `Always use private browsing mode`, but it's a fake:
 > Firefox 20 introduced per-window private browsing mode, in which private
 user data is stored and accessed concurrently with public user data from
 another window.
  from https://developer.mozilla.org/EN/docs/Supporting_per-
 window_private_browsing
 So, Mozilla exposes it to users as `private browsing mode` which means by
 default the mode for the whole browser (that was described in
 https://wiki.mozilla.org/Firefox3.1/PrivateBrowsing/FunctionalSpec), but
 explains to developers that it's a `per-window private browsing mode`
 which means private browsing isolated to a window (it's a lie too, proof:
 https://bugzilla.mozilla.org/show_bug.cgi?id=117222).
 In fact, it's a Tabbed Private Browsing where `mode` means mode of its
 operation for all windows instead of for window:
 > The implementation should support per-tab private browsing as an
 implementation detail, but that functionality will not be exposed by
 default.
  from https://wiki.mozilla.org/Per-window_Private_Browsing

 Drawbacks are still being discovered here and there:
 official - https://developer.mozilla.org/EN/docs/Supporting_per-
 window_private_browsing#Forcing_a_channel_into_private_mode,
 > down side is the global state is lost, there is no global 'private
 browsing' flag in the new implementation
  from https://wiki.mozilla.org/Security/Reviews/PerWindowPrivateBrowsing,
 Interaction of Clear Recent History dialog and the private browsing mode
 https://bugzilla.mozilla.org/show_bug.cgi?id=463607,
 > The cookie viewer open from private-window shows the cookie which is
 stored in normal browsing window.
  from https://bugzilla.mozilla.org/show_bug.cgi?id=823941,
 etc...

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20491>
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