What's new in version 1.5.4

The Facebook plugin for WordPress has been updated to support the latest features of the Facebook Like Button, Facebook Embedded Posts, and Facebook SDKs.

Facebook Like with Share

Facebook introduced a new Like Button design with a Share button replacing the previous Send button option. The send button option has been removed from the Like Button settings page; passing a send button setting to the Like Button markup builder will have no effect.

Embedded Post custom width

Facebook Embedded Posts now support a custom width between 350 and 750 pixels. If your theme sets a content width the Facebook Embedded Post width will adjust for your theme. Pass a custom width between 350 and 750 pixels to the facebook_embedded_post shortcode to customize the width of a specific embedded post.

Facebook SDK updates

The Facebook SDK for JavaScript now requires either native support for HTML5 postMessage or Flash 8.0.24 or newer to help facilitate cross-domain communication. The previous channelUrl parameter passed to the JavaScript SDK is invalid; the file and parameter have been removed.

The Facebook SDK for PHP has been updated to the latest version: 3.2.3. The Facebook plugin for WordPress initializes the Facebook SDK for JavaScript with an allowSignedRequest value of false. If you are extending the Facebook plugin for WordPress for use with a Facebook canvas application you should adjust your initialization of the Facebook SDK for PHP packaged with the Facebook plugin for WordPress.

http://wordpress.org/plugins/facebook/