Why does outlook sign me out when I try to login using firefox?

[NOTE: Please limit answers to Microsoft employees only]

Whenever I try to login to outlook (regardless of browser used), I get:

You signed out of your account

It's a good idea to close all browser windows.

I realize there is a work-around by deleting website data in the browser, however, this isn't a problem the user should be fixing. I believe Microsoft should be looking into this. Even when website data is deleted, it the problem keeps resurfacing almost every couple of days. Can't Microsoft do anything about this? <this is the primary question.

Thanks