In a security advisory on its website, Tor advises users to switch away from Windows to ensure anonimity. The advice comes after the discovery of a vulnerability in Firefox that enables hackers (and government agencies) to discover identifying information about Tor users. Full details can be read over here.
WHAT TO DO:
First, be sure you're running a recent enough Tor Browser Bundle. That
should keep you safe from this attack.
Second, be sure to keep up-to-date in the future. Tor Browser Bundle
automatically checks whether it's out of date, and notifies you on its
homepage when you need to upgrade. Recent versions also add a flashing
exclamation point over the Tor onion icon. We also post about new
versions on the Tor blog: https://blog.torproject.org/
Third, realize that this wasn't the first Firefox vulnerability, nor
"S" beside the green onion, and select "Forbid Scripts Globally").
like you expect. A future version of Tor Browser Bundle will have an
You might also like Request Policy . And you might want to randomize
your MAC address, install various firewalls, etc.
Fourth, consider switching to a "live system" approach like Tails .
Really, switching away from Windows is probably a good security move
for many reasons.
And finally, be aware that many other vectors remain for vulnerabilities
big vectors exist, like css, svg, xml, the renderer, etc. We need
help improving usability of (and doing more security analysis of)
better sandboxing approaches  as well as VM-based approaches like
Whonix  and WiNoN . Please help!