Tor Project issued a security advisory over the weekend after an attack targeted users of the Tor Browser. The attack exploited a Firefox JavaScript vulnerability that has already been resolved. The vulnerability is a cross-platform threat, but the exploit in this case was Windows-specific. Tor Browser users on Linux, OS X, and LiveCD systems like Tails were never at risk of exploit. The Tor Browser is a modified version of the Mozilla Firefox browser that gives users the ability to browse anonymously through Tor without having to do any real configuration.
Source: https://threatpost.com/tor-urges-users-to-leave-windows/101825/