Brave Browser is fixing a privacy issue that leaks the Tor onion URL addresses you visit to your locally configured DNS server. Brave’s ‘Private Window with Tor’ mode acts as a proxy to the Tor network. Brave has disabled the CNAME ad blocking feature that blocks third-party tracking scripts that use CNAME DNS records to impersonate a first-party script. Brave is aware of this bug as it was reported on their GitHub project page eighteen days ago, and developers have already created a fix.
Source: https://www.bleepingcomputer.com/news/security/brave-privacy-bug-exposes-tor-onion-urls-to-your-dns-provider/