Github (and Bitbucket as well) expose the vast majority of their users’ email addresses via commit metadata.

As a proof-of-concept, I made a single page app using Angular + the Github API to demonstrate how browse-able/scrape-able this contact information is.

Live demo here.

Github Email Thief

You can check if your Github username is affected.

You can read about how to hide your email address here.

The project is non-commercial and MIT-licensed.