Yahoo also owns Flickr and Tumblr, but no Tumblr accounts have been reported as compromised. Flickr users’ accounts may be at risk, because the site uses Yahoo credentials. While credentials may be at risk, no Flickr accounts have been formally reported as compromised.
Yahoo indicated plans of contacting affected users. Even if they are not contacted, Yahoo users are encouraged to update their usernames, passwords, security questions and the credentials of any additional accounts linked to their Yahoo credentials.