Brave before 1.34, when a Private Window with Tor Connectivity is used, leaks .onion URLs in Referer and Origin headers. NOTE: although this was fixed by Brave, the Brave documentation still advises "Note that Private Windows with Tor Connectivity in Brave are just regular private windows that use Tor as a proxy. Brave does NOT implement most of the privacy protections from Tor Browser."
CWE-200