[tbb-bugs] #24056 [Applications/Tor Browser]: UI locale is detectable by button width

Mon Oct 30 11:16:48 UTC 2017

#24056: UI locale is detectable by button width
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     Reporter:  gk                        |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  High                      |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Major                     |   Keywords:  tbb-fingerprinting
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
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 We got a HackerOne report by xiaoyinl outlining steps to detect the UI
 locale of the browser despite the user not changing the `Accept` header:

 If one specifies a button `<input type="submit">` without a "value"
 property, the default text of the button depends on the UI language. And
 the resulting width of the button can be measured.

 We should not only focus on that particular button but should look closer
 whether other UI parts are suffering from the same problem.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24056>
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