Recently I have disabled the option to allow third party cookies in Firefox. Immediately, I noticed that when I log in to Sharepoint/Office 365, the login seems successful, and redirects me to the home page as normal, but it seems to initiate a refresh of the page when the content has loaded.
Enabling third party cookies again fixes the problem. However, as I don't want third party cookies enabled on all sites, I have tried adding some cookies to the exceptions list, by first clearing all cookies from my browser, then finding whatever tries to get set from the login process. Despite adding what I saw, the problem still persists. There must be a cookie that I am missing, but I don't know what it is.