Brave does block requests to the localhost if you don't consent to it, so it did successfully protect users from this tracking. Researchers say Yandex has been doing this since February of 2017 on ...

In this case, to resolve the issue, you can access the local web server by specifying the port number – to do that, you have to type localhost:8080 in your browser. 3] Change Apache port in XAMPP ...

In the researcher's words, “These native Android apps receive browsers' metadata, cookies and commands from the Meta Pixel and Yandex Metrica scripts embedded on thousands of websites. These ...

The short explanation is that web sites can open connections to localhost. And on Android, apps can be listening to those ports, allowing web pages to talk to apps.