LinkedIn has confirmed that some of the passwords that were compromised correspond to LinkedIn accounts. LinkedIn members will receive an email from LinkedIn with instructions on how to reset their passwords. The affected members will also receive a second email from our Customer Support team explaining why they are being asked to change their passwords and how to do it. LinkedIn is continuing to investigate this situation and is adding new security to its password databases. It is worth noting that the affected members who update their passwords will benefit from the enhanced security we just recently put in place.”]
Source: https://blog.linkedin.com/2012/06/06/linkedin-member-passwords-compromised