This Site's Been Breached! per sitehasbeenbreached

This extension is a tool to notify you if the site you're currently visiting has been affected in a data breach recently. If so, This Site's Been Breached! will provide some context on the breach, as well as an estimate of how many people may have been affected. This extension is designed to be used as a nudge to reset your password on sites where your account may have become vulnerable. Additionally, once you've looked at a breach warning, you have an option to dismiss it. The extension will automatically detect if a breach dismissal has fallen out-of-date (because there was another breach), and show the warning again if appropriate.