[tor-bugs] #26381 [Applications/Tor Browser]: about:tor page does not load on first start in localized Windows bundle

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#26381: about:tor page does not load on first start in localized Windows bundle
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 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:  new
 Priority:  Very High                            |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-torbutton, ff60-esr,             |  Actual Points:
  TorBrowserTeam201806                           |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by mcs):

 Tracking down the root cause of this is proving to be challenging. My
 Windows debugging skills seem to be inadequate, especially when the
 browser is running in multiprocess mode. Here are some additional things
 that Kathy and I learned:
 * In addition to the undefined entity bug, sometimes a blank page is
 loaded instead of about:tor. When a blank page is loaded, that tab is
 useless (all pages silently fail to load, including internal pages such as
 about:config).
 * The problems with about:tor do not always occur. They seem to occur
 every time with a clean install or when running with
 TOR_FORCE_NET_CONFIG=1.
 * When about:tor does not load correctly, Wextensions (all) do not work
 either. This points to some kind of race or other bug during
 initialization.
 * Reducing the sandbox level makes these problems disappear: if I set
 `security.sandbox.content.level` to `2` about:tor loads correctly every
 time, but a setting of `3` or higher causes problems.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26381#comment:9>
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