Mozilla's latest Firefox 17 Web browser has been released and includes a host of intriguing new features, including the integration of Facebook Messenger into the browser to give users a seamless mix of Web searching and real-time communications.

The new Facebook Messenger integration, which is the first new service to come out of Mozilla's new Social API project, is optional and must be turned on by the user, according to a Nov. 20 post on The Mozilla Blog. So far, the Facebook integration is a preview into the fledgling service, and more capabilities and features will be added.

"Much like the OpenSearch standard, Mozilla's new Social API lets social services integrate into Firefox in a compelling way and makes it easier to use the Web the way you want," said the blog post. "The Social API includes features like a social sidebar, toolbar notification buttons and the ability to easily chat with your friends no matter where you are on the Web."

The new Facebook integration will mean that users will be able to keep up with friends and family without having to switch between or open new tabs. Users will be able to stay connected to integrated social media sites while they are Web searching, watching a video or playing a game, according to Mozilla.

To use the new preview version of the service, users can download or upgrade and install the new, free latest Firefox 17 and then visit the Facebook Messenger for Firefox page and click "Turn On."

Users will then get a social sidebar with their Facebook chat and updates, photo tags and notifications for messages, friend requests and more. Users will be able to respond right from their Firefox toolbars instead of having to open a Facebook tab in Firefox.

"Today's Social API is just the beginning of making Firefox more social," according to Mozilla officials. "We'll soon add support for more features and multiple providers. We'll also be listening to feedback from our early users to understand how Firefox can do more to keep them connected to their social lives online."

Also new in Firefox 17 is a security feature that makes it easier for users to know when their third-party add-ins must be updated to protect their computers from malicious applications. The "click-to-play plug-in blocks" will now pop up on users' screens to notify them that they have to update any browser add-ons that are out-of-date. The feature has been in beta and is now included in Firefox 17.

The latest Firefox 17 also includes an updated Awesome Bar with larger icons while dropping support for Mac OS X 10.5.

Mozilla officials hope that they have prepared this latest release for a flawless debut after running into serious security problems that caused Mozilla to temporarily remove Firefox 16 from its download page in October, just two days after the Oct. 9 release of Firefox 16.

The Mozilla team discovered a serious security flaw on Oct. 10, a day after the global release of Firefox16. The problem involved a vulnerability that could allow a malicious site to potentially determine which Websites users have visited and have access to the URL or URL parameters.

Less than 24 hours later, the vulnerability was repaired and Firefox 16 was again made available for downloads and upgrades. Mozilla's reaction to the flaw was to take no chances and to pull the new release back so it could be fixed.

The original Firefox 16 release unveiled by Mozilla Oct. 9 was touted by the company for having several new features, including default VoiceOver support on Mac OS X, as well as initial Web app support for Windows, Mac and Linux. Also included were 16 bug fixes, including 11 that were rated as critical and three that were rated as high impact.

Firefox browsers hold about 19.9 percent of the global browser market, compared with 54.1 percent for Microsoft's Internet Explorer browser, according to October figures from Web analysis firm Net Applications. Google's Chrome holds 18.5 percent, while Safari has about 5.2 percent.