[tbb-bugs] #17207 [Tor Browser]: Testing navigator.mimeTypes for known names can reveal info and increase fingerprinting risk

[Tor Bug Tracker & Wiki]

#17207: Testing navigator.mimeTypes for known names can reveal info and increase
fingerprinting risk
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     Reporter:  TemporaryNick  |      Owner:  tbb-team
         Type:  defect         |     Status:  needs_information
     Priority:  normal         |  Milestone:
    Component:  Tor Browser    |    Version:
   Resolution:                 |   Keywords:  tbb-fingerprinting
Actual Points:                 |  Parent ID:
       Points:                 |    Sponsor:
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Comment (by teor):

 In Tor Browser 5.0.3 on OS X 10.10.5, I can't retrieve the length
 `navigator.mimeTypes.length` or list of members `navigator.mimeTypes`.

 But I can query for a member (as TemporaryNick describes).

 Can you try the attached script with `if (navigator.mimeTypes.length > 0)
 {` and the corresponding brace commented out?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17207#comment:5>
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