  Mixed Reality (MR) devices require a world with always-on sensors and
real-time processing applied to their outputs. We have grappled with some of
the ethical concerns presented by this scenario, such as bystander privacy
issues with smartphones and cameras. However, MR technologies demand that we
define and defend privacy in this new paradigm. This paper focuses on the
challenges presented by eye tracking and gaze tracking, techniques that have
commonly been deployed in the HCI community for years but are now being
integrated into MR devices by default.
