[tbb-bugs] #20025 [Applications/Tor Browser]: document.characterSet enables fingerprinting of localization (only with HSTS?)

[Tor Bug Tracker & Wiki]

#20025: document.characterSet enables fingerprinting of localization (only with
HSTS?)
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 Reporter:  dcf                       |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  tbb-fingerprinting        |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by dcf):

 I checked and the same HSTS weirdness happens with stock Firefox 45.3.0.
 To reproduce, go to Preferences → Content → Fonts & Colors → Advanced →
 Text Encoding for Legacy Content, and select Korean. Then the HSTS demo
 page https://people.torproject.org/~dcf/tor20025/check-charset.html will
 show `EUC-KR` for document.characterSet. The non-HSTS demo page
 https://people.eecs.berkeley.edu/~fifield/tor20025/check-charset.html
 continues to show `windows-1252`.

 Chromium 52.0.2743.116 doesn't appear to make a difference between HSTS
 and non-HSTS. Go to Settings → Web content → Customize fonts → Encoding
 and change to Korean. Both demo pages show `EUC-KR`.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20025#comment:2>
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