The extension is called 'Password Checkup,' and has exactly one purpose. It securely checks your logins against a breach database in real time as you're logging onto the various websites you use daily.
Note that the plugin checks both passwords you enter manually and those stored in Chrome's password manager.
It's a brilliant feature, although not without risks. After all, it opens up the possibility that during the check procedure, your password could be detected by a hacker monitoring your device. Even so, the risks of that happening are quite small, while the benefits gained via getting real time information about whether your passwords have been compromised is too big to ignore.
The central issue is this: Over the past several years there have been scores of high-profile data breaches that have seen literally billions of user ID's and credentials exposed, most of which wind up for sale on the Dark Web. Worse, most users are blissfully unaware of the fact that their credentials have been compromised. This extension changes that, giving you an opportunity right then and there to change your password.
The development team is constantly updating the massive database that the extension uses to check for compromised passwords, and they've got plans to extend the use of the API's capabilities down the road. They're even shopping for suggestions from Google's vast user base on how best to use it in future projects.
Overall, despite the fact that the new extension opens up potential for abuse, the availability of the new capability is hailed as a great step toward better security. Grab a copy today.