AshleyMadison

In July 2015 a group calling itself The Impact Team breached the dating service Ashley Madison. The attackers demanded the site be shut down and later released over 60GB of customer data. The breach exposed millions of users who were seeking extramarital affairs. The leaked information included account details names and hashed passwords. While the full dump was massive the most commonly circulated versions contain subsets of the user credentials and personal identifiers. This incident is considered one of the most significant privacy breaches due to the sensitive nature of the service.