Like if I'm logged out on battlelog.battlefield.com, but logged in on origin.com, as soon as I click LOG IN, it instantly performs the login without me having to enter my username or password.

What is happening?

(no this isn't lastpass logging me in automatically)

2 Answers 2


It could be the site uses a single sign-on system like SAML or likewise. You'll have a cookie for the main authentication endpoint, but not the subdomain. When you press login you're redirected to the main authentication endpoint with the subdomain as a parameter to the request. The single sign-on system sees you're already authenticated and either sends you back to the subdomain's authentication endpoint with a "yes, this user is authenticated" or sets a cookie for the subdomain (minor hackery which doesn't happen too often).

This diagram describes it: https://docs.wso2.com/download/attachments/28707597/saml-diagram.png The subdomain would be the service provider, the main authentication endpoint would be the identity provider. (Sorry for the blatant branding, it was the simplest diagram I could find :))


They usually use cookies in Log in system. Some sites provides you to push "submit" button but others make you log in automatically. Check the website cookie policy, there are the answer

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