Quoting from the MyHeritage.com Blog article entitled "MyHeritage Statement About a Cybersecurity Incident,"
Today, June 4, 2018 at approximately 1pm EST, MyHeritage’s Chief Information Security Officer received a message from a security researcher that he had found a file named myheritage containing email addresses and hashed passwords, on a private server outside of MyHeritage. Our Information Security Team received the file from the security researcher, reviewed it, and confirmed that its contents originated from MyHeritage and included all the email addresses of users who signed up to MyHeritage up to October 26, 2017, and their hashed passwords.If you are registered with MyHeritage, please read the entire article. Here is the scope of the breach,
We believe the intrusion is limited to the user email addresses. We have no reason to believe that any other MyHeritage systems were compromised. As an example, credit card information is not stored on MyHeritage to begin with, but only on trusted third-party billing providers (e.g. BlueSnap, PayPal) utilized by MyHeritage. Other types of sensitive data such as family trees and DNA data are stored by MyHeritage on segregated systems, separate from those that store the email addresses, and they include added layers of security. We have no reason to believe those systems have been compromised.Please follow the instruction in the blog post to change your password. See