Patrick Lai

XLogin enhances the WordPress login page (usually wp-login.php) to 
allow users to authenticate with the following external services:
<ul>
<li>Facebook Login</li>
<li>Google Sign-In</li>
<li>Yahoo! OAuth</li>
</ul>
These services can be enabled or disabled individually. XLogin adds a 
button to the WordPress login page for each enabled service. Clicking 
the button sends the browser to the corresponding external service 
where the user can authorize the WordPress site to access their 
information. Having been granted access to, for example, the Facebook 
public profile of a user, XLogin retrieves their email address to 
find a matching WordPress user to complete the login process.
XLogin also maintains a list of external aliases. They are additional 
email addresses for mapping to WordPress users. Some scenarios where 
external aliases can be handy include:
<ol>
<li>
A user’s email address in his WordPress profile is not used in any 
of the external services. For example, a corporate WordPress site 
may mandate the use of company email addresses in user 
profiles. If a user has for example his Gmail address in the 
external alias list, they can still nevertheless sign in Google.
</li>
<li>
A WordPress user account is shared by a group of actual 
users. With XLogin it is not necessary to have the users share a 
single password. Instead just register their email addresses (as 
known by the external services) as external aliases; it becomes a 
simple matter to add and remove user.
</li>
</ol>
XLogin has the option to restrict an external service to only users with 
external aliases. This allows tight control on who can use external 
services to login.
A user’s profile in WordPress and in the external service may be 
different. Email address is one, and display name (or its component 
family and given names) is another. XLogin offers the option to import 
the external profile information into the current session. The imported 
display name will be tagged with the external service name. For 
example, if a user has display name ‘John Doe’ in WordPress, but is 
known as ‘Johnny D’ in his Facebook account, then he would be 
displayed as ‘Johnny D (Facebook)’ (instead of ‘John Doe’) in his 
WordPress session when he logs in with Facebook.
Finally XLogin has the notion of ‘guest’ user. When an email address 
provided by an external service does not correspond to a specific 
WordPress user, XLogin will proceed with a guest WordPress user 
configured for the service. There are plugins that control access to 
content based on user roles; a site can combine such with XLogin to 
control what is visible to guests. Note that guest WordPress users 
should have minimal privileges. XLogin has safeguards to ensure, for 
example, that a guest cannot edit posts. It also filters out guest’s 
permission to access the dashboard or to update their own profile.

XLogin

Login to WordPress with external services like Facebook, Google, and Yahoo.

thenbrent

Looking for maintainers. This plugin is currently not maintained. If you would like to take over the development please let me know using the plugin support forum or GitHub issue system.
WordPress Social Login is a good alternative to this plugin:
https://wordpress.org/plugins/wordpress-social-login/
Social Connect adds social login buttons on the login, register and comment forms of your WordPress site.
The buttons offer login and registration using a Twitter, Facebook, Google, Yahoo or WordPress.com account.
It makes it super easy for new members to register with your site and existing members to login.
<h4>Props</h4>
Special thanks to:
<ul>
<li><a href="https://wordpress.org/support/profile/markusdrake" rel="ugc">markusdrake</a> for patches and helping in the support forums;</li>
<li><a href="https://wordpress.org/support/profile/enochfung" rel="ugc">L D</a> for patches and helping in the support forums;</li>
<li><a href="https://wordpress.org/support/profile/geodanny" rel="ugc">Geodanny</a> for helping in the support forums; and</li>
<li><a href="http://blog.wirone.info/" rel="nofollow ugc">Wirone</a> for polish translation and patches.</li>
</ul>
And everyone else in the forums sharing the fixes they find and answering each others questions.
<h4>Contribute</h4>
Social Connect is rapidly growing in popularity and help with the growing pains is appreciated.
If you’re a developer, you can contribute fixes & optimisations via <a href="https://github.com/thenbrent/social-connect" rel="nofollow ugc">Social Connect on GitHub</a>.
Everyone can help out by answering questions in the <a href="https://wordpress.org/tags/social-connect?forum_id=10#postform" rel="ugc">Support Forums</a>.

Social Connect

Allow your visitors to comment, login and register with their Twitter, Facebook, Google, Yahoo or WordPress.com account.

XLogin vs Social Connect