When does Firefox alert for breached sites? – Mozilla Security Blog

Mozilla’s Position on Data Breaches Data breaches are common for online services. Humans make mistakes, and humans make the Internet. Some online services discover, mitigate, and disclose breaches quickly. Others go undetected for years. Recent breaches include “fresh” data, which means victims have less time to change their credentials before they are in the hands of attackers. While old breaches

[Rockridge]

Fx63：ユーザーが過去に情報流出のあったサイトを訪れると通知がされるようになった。最初の通知は過去12か月にHave I Been Pwned（HIBP）に追加されたサイトで、以後の通知は過去2か月にHIBPに追加されたサイトで行われる。