Is the issue with not being able to unlink Xbox accounts from Activision accounts being addressed?

My boyfriend downloaded the Modern Warfare beta on my Xbox, and signed into his Activision account on my gamertag. After both buying the game yesterday, I created my own Activision account and linked my Xbox account to it. Once I launched Modern Warfare on the Xbox, the Account Summary page came up with all of his information listed. I clicked on Account Settings to change it to mine, and a login screen came up. I tried entering my Activision Account credentials, and nothing happened, it just kicked me back to the home screen. When trying to unlink the accounts online via Activision, it says unlinking is unavailable for the Xbox platform.

Aside from that, when I try to log in to the account I created literally last night, it won't accept my password. I clicked on the reset password button, and haven't received any email to reset it. Assuming my account magically disappeared, I clicked on Sign Up to try again. It asks me to choose my platform. I click on Xbox, and it doesn't ask for any credentials, just auto logs in to his Activision account, and takes me to the Activision home page, signed in as him. This seems like a security concern. Why is it signing into someone else's account without asking for a password, or even going to a log in screen? I'm creating a brand new Activision account and it won't let me put in a new Xbox account to be associated with it (his usernames are linked to his Activision account which already exists). **Note that none of these passwords are "saved" on my laptop

Edit: I have tried deleting browser cookies, and that doesn't stop the auto log in issue