It's no secret that Brave started injecting affiliate id's on some links some time back. These affiliate programs (Binance, Coinbase, Ledger, Trezor) allow Brave to view a detailed overview of purchases made by everyone who signed up to these services using Brave.

ETA: Don't take my word for it:

https://gizmodo.com/brave-blows-up-its-whole-reason-for-exis...

https://www.androidpolice.com/2020/06/07/brave-browser-caugh...