Tor silently, last October, quit spoofing OS and now reports over browser headers what OS you are.

Previously, every Tor Browser was "windows".

The claim I've heard was that there were JavaScript attacks that could uncover what OS you were using. Patching those would be 'too hard'. So now TBB just gives up OS. Seems not very good to voluntarily give up bits of PII.

https://m.youtube.com/watch?v=3wlNemFwbwE is where I was made aware of this problem. I verified it on my infrastructure too.