For login to Stack Overflow I use Yahoo's OpenID service. Today, I tried to register on Stack Overflow with my Facebook account. When I allowed Facebook to give my information to Stack Overflow, I was logged in to my Yahoo account.

In this case, Stack Overflow used my email to register me and my email was in the Stack Overflow users database so I logged in to main account (Yahoo) and now I have two OpenID acounts.

When a user has not confirmed his email on Facebook, is this process also correct? If yes, some users can login to another account with faked Facebook account to the Stack Overflow.

Note: I don't know how we could check status of email on Facebook account with Facebook Graph API. My question on Stack Overflow is Is a user's email address confirmed in Facebook Graph API?

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    Interesting question, but I'm sure Facebook don't use an E-Mail address for OpenID before having confirmed it. – Pekka Aug 6 '12 at 18:00
  • <3 internet in 2012. – Filip Dupanović Dec 15 '12 at 20:46

You can't sign into Stack Exchange (or anything actually) with Facebook without having confirmed your email address.

You get a message that looks something like this:

enter image description here

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