[tor-bugs] #19844 [- Select a component]: Prevent browser history leaks from CSS mix-blend-mode API in Tor Browser

[Tor Bug Tracker & Wiki]

#19844: Prevent browser history leaks from CSS mix-blend-mode API in Tor Browser
--------------------------------------+-----------------------------
     Reporter:  isis                  |      Owner:
         Type:  enhancement           |     Status:  new
     Priority:  Medium                |  Milestone:
    Component:  - Select a component  |    Version:
     Severity:  Normal                |   Keywords:  tbb-linkability
Actual Points:                        |  Parent ID:
       Points:                        |   Reviewer:
      Sponsor:                        |
--------------------------------------+-----------------------------
 Similar to the old trick of querying the colour of a link on a page to see
 whether the user has visited that link before, there is
 [https://lcamtuf.blogspot.sk/2016/08/css-mix-blend-mode-is-bad-for-
 keeping.html a new form of this attack] which is made more efficient by
 querying the :visited attribute on a set of numerous links via defining a
 boolean algebra with the non-linear CSS blending operators in the
 [https://developer.mozilla.org/en-US/docs/Web/CSS/mix-blend-mode mix-
 blend-mode API].

 lcamtuf has [http://lcamtuf.coredump.cx/whack/ a demo of the attack] which
 works in my Tor Browser 6.0.3. We should determine a way to mitigate this
 attack.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19844>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online