[tor-bugs] #30605 [Applications/Tor Browser]: accept-language header leaks browser localization

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#30605: accept-language header leaks browser localization
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     Reporter:  sysrqb                    |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  Medium                    |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Normal                    |   Keywords:
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
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 A [https://blog.torproject.org/comment/281830#comment-281830 blog user]
 mentions each request includes the chosen browser language. Do we
 normalize this on desktop such that we only send `en-US` regardless of the
 browser's localization?

 Using https://wtfismyip.com/headers

 With `en-US` as the browser locale:
 {{{
 host: wtfismyip.com
 connection:
 close user-agent: Mozilla/5.0 (Android 6.0; Mobile; rv:60.0)
 Gecko/20100101 Firefox/60.0
 accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
 accept-language: en-US,en;q=0.5
 accept-encoding: gzip, deflate, br
 upgrade-insecure-requests: 1
 }}}


 With `ru-RU` as the browser locale:
 {{{
 host: wtfismyip.com
 connection: close
 user-agent: Mozilla/5.0 (Android 6.0; Mobile; rv:60.0) Gecko/20100101
 Firefox/60.0
 accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
 accept-language: ru,ru-RU;q=0.8,en-US;q=0.5,en;q=0.3
 accept-encoding: gzip, deflate, br
 upgrade-insecure-requests: 1
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30605>
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