An anonymous reader writes: Mozilla engineers are working on a notifications system for Firefox that shows a security warning to users visiting sites that have suffered data breaches. The notifications system will use data provided by Have I Been Pwned?, a website that indexes public data breaches and allows users to search and see if their details have been compromised in any of these incidents. Work on this project has only recently started. The code to show these warnings is not even in the Firefox codebase but managed separately as an add-on available (on GitHub). The alert also includes an input field. In the add-ons current version this field doesn't do anything, but we presume it's there to allow users to search and see if their data was exposed during that site's security breach. Troy Hunt, Have I Been Pwned's author has confirmed his official collaboration with Mozilla on this feature.