  When working with Git, a popular version-control system, email addresses are
part of the metadata for each individual commit. When those commits are pushed
to remote hosting services like GitHub, those email addresses become visible
not only to fellow developers, but also to malicious actors aiming to exploit
them.
  As a part of our research we created a tool that leverages the publicly
available GitHub API to collect user data. Analysis of this data not only gives
access to millions of email addresses in very little time, but is also powerful
and dense enough to create targeted phishing attacks posing a great threat to
all GitHub users and their private, potentially sensitive data. Even worse,
existing countermeasures fail to effectively protect against such exploits.
  As a consequence and main conclusion of this paper, we suggest multiple
preventive measures that should be implemented as soon as possible. We also
consider it the duty of both companies like GitHub and well informed software
engineers to inform fellow developers about the risk of exposing private email
addresses in Git commits published publicly.

Cryptography and Security