On 9/12/2016 9:41 AM, [email protected] wrote:
https://www.browserleaks.com/firefox
it can be used for both fingerprinting (different users use different OS setups
or different Tor versions) and exploiting software vulnerabilities because when
attacker don’t know your OS or browser version they don’t know what payload can
do the thing that if be used incorrectly will show a download warning that
compromises their valuable malware to citizenlab like groups.
Using TBB, I looked at the link - browserleak.com/firefox - with JS
disabled. The code that supposedly detects values in firefox.js giving
away the OS.
10. var el = document.createElement("script");
11. el.type = "text/javascript";
12. el.onload = load;
13. el.onerror = err;
14. document.head.appendChild(el);
15. el.src = "resource:///defaults/preferences/firefox.js";
16. }
17.
18. var pref,
19. sticky_pref,
20. os;
21.
22. pref = sticky_pref = function(key, val) {
23. if (!os)
24. if (key == "browser.gesture.pinch.out" && val == "cmd_fullZoomEnlarge")
25. os = "Windows";
26. else if (key == "browser.backspace_action" && val == "2")
27. os = "Linux";
28. else if (key == "browser.gesture.pinch.threshold" && val == "150")
29. os = "Mac";
30. var include = function(load, err) {
31. }
32.
33. include(function() {
34. console.log( "OS: " + (os ? os : "unknown") );
35. },function() {
36. console.log( "OS: n/a (not a Firefox)" );
37. });
38. </script>
The prefs & values the code is querying appears in about:config, as
would many firefox.js settings.
Question for devs / Firefox experts: many prefs are reported to sites
so they can display content, but are they allowed to access every
setting in about:config - default or user set?
This can't be correct. That would make users very unique.
Is this bug somehow supposed to allow only querying firefox.js values &
no other files? Why is that? If allowed access to firefox.js, why not
all firefox files?
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