User-agent OS info leak
Tor Browser 8.0 on Linux has user-agent Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
This behavior can aid fingerprinting or vulnerability exploitation.
Tor Browser 7.x.x and before had one single Windows user-agent even on Linux platforms, only Android (Orfox) had other UA.
Trac:
Username: time_attacker