Yahoo was one of the sites affected by the Heartbleed bug discovered earlier this month. In an article posted in Yahoo Help Central, and last updated on April 11, 2014, they report their “ team has successfully made the appropriate corrections across our entire platform.”
While they did not suggest users change their passwords as an added security and they do not mention whether or not a security breach was detected, they include a link with instructions on changing passwords below the article for those concerned about security.
Several other sites including Pinterest and Tumblr contacted users by email to notify them of the vulnerability and suggested users change their passwords as an added security. It is unclear whether Yahoo contacted any users regarding the vulnerability, however, as with all other affected sites and maintaining account security, it is a good idea to change your passwords as an added security.