Mac and Linux versions of the Tor anonymity browser just received a temporary fix for a critical vulnerability that leaks users’ IP addresses when they visit certain types of addresses.
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.
“The fix we deployed is just a workaround stopping the leak,” Tor officials wrote in a post announcing Friday’s release. “As a result of that navigating file:// URLs in the browser might not work as expected anymore. In particular entering file:// URLs in the URL bar and clicking on resulting links is broken. Opening those in a new tab or new window does not work either. A workaround for those issues is dragging the link into the URL bar or on a tab instead. We track this follow-up regression in bug 24136.”