What information is being accessed by a third party that supports “log in with Google”?

Question

There are some applications that you can add to Google Chrome.

However, some of them require you to log in to a Google account. During that process you get a message along the lines of "xxx is asking for some information from your Google account". You're given the option to approve or deny. And an option to remember the approval.

What information is it accessing or can it access? I'm wanting to know if this a potential security problem.

Answer 1

I've found the answer.

Google login is based on OpenID which they call "Federated Login".
See this link: Authentication and Authorization for Google APIs

What could be exchanged is through the OpenID attribute exchange protocol? Currently, Google only supports the following attributes (see section "Attribute exchange extension" in the provided link)

• country
• email
• firstname
• language
• lastname

So to answer the second part of my question, about it being a security problem. Well, only if you want to keep the information in those fields private.