You can now review and manage your browser and GitHub Mobile sessions using the new Sessions tab in your user settings. This new tab includes all of your signed-in web sessions, as well as each GitHub Mobile app your account is signed into. You can revoke each web and mobile session individually. For mobile sessions, this signs you out of the GitHub Mobile app on that device, and disables that application for use as a second factor. The new Sessions tab replaces the web sessions view that was present under Password and authentication.
This new settings page is generally available for GitHub.com users now, and will be released to GitHub Enterprise Server as part of GHES 3.8.
To learn more, see "Viewing and managing your sessions".