We are currently evaluating this issue and will update this article when we have more information. In the meantime, follow these steps:

Please do an advanced search and paste the below into the search box:

((SELECT COUNT (contactsx1.social_security_no_hash) from contacts as contactsx1 where contactsx1.social_security_no_hash is not null and contactsx1.social_security_no_hash <> '' and contactsx1.social_security_no_hash=contacts.social_security_no_hash group by contactsx1.social_security_no_hash) > 1)