We’ve rolled back our latest update which caused users to receive a login prompt inside of SharePoint. To apply the fix to your SharePoint environment, simply update Masthead. Once you open your Masthead Installer, you should receive a prompt to update to 18.104.22.168. Once done, users should no longer receive a login prompt. They may need to refresh their browsers for the update to go to into effect.
Updated on October 25, 2018