Submitted via IRC for SoyCow1984
TorMoil, as the flaw has been dubbed by its discoverer, is triggered when users click on links that begin with file:// rather than the more common https:// and http:// address prefixes. When the Tor browser for macOS and Linux is in the process of opening such an address, "the operating system may directly connect to the remote host, bypassing Tor Browser," according to a brief blog post published Tuesday by We Are Segment, the security firm that privately reported the bug to Tor developers.
On Friday, members of the Tor Project issued a temporary work-around that plugs that IP leak. Until the final fix is in place, updated versions of the browser may not behave properly when navigating to file:// addresses. They said both the Windows versions of Tor, Tails, and the sandboxed Tor browser that's in alpha testing aren't vulnerable.
(Score: 2) by urza9814 on Wednesday November 08 2017, @12:48AM
Agree with you about Javascript not always being disabled, but it's far worse than just rewriting links. If it rewrites the link to 'file:///...', you'd know *something* weird happened. Even if you didn't know exactly what or why, you'd notice.
But I wonder if this flaw would still exist if the link is opened directly through a Javascript call. It won't open a browser tab, it won't redirect the page, it'll just fire a request to 'file:///whatever' and discard the response...but meanwhile your IP potentially gets exposed without you knowing anything happened at all. And without you clicking any link.
This was IMO one of the great advantages of the old* Freenet network. No scripts to expose information and no servers to retrieve it. No active content was supported at all, and you didn't connect to a server you just retrieved static files from a distributed storage system.
* I say "old" Freenet because I stopped using back during the 0.5/0.6 network split which was nearly a decade ago now. Based on the idiocy of some of those devs I wouldn't be surprised if they "fixed" that at some point...