At Yahoo! we take security very seriously and invest heavily in protective measures to ensure the security of our users and their data across all our products.
We confirm that an older file from Yahoo! Contributor Network (previously Associated Content) containing approximately 450,000 Yahoo! and other company users names and passwords was compromised on July 11.
Of these, less than 5% of the Yahoo! accounts had valid passwords. We are taking immediate action by fixing the vulnerability that led to the disclosure of this data, changing the passwords of the affected Yahoo! users and notifying the companies whose users accounts may have been compromised.
We apologize to all affected users. We encourage users to change their passwords on a regular basis and also familiarize themselves with our online safety tips at security.yahoo.com.