Note: Wordpress officially has not announce yet any security breach news on their website, but these warning mails are silently received by compromised account holders. Method of hack is still not confirmed. But hacking 15000 blogs from wordpress server and posting same article on all sites most obvious can't be a client side hack. Either wordpress servers has been compromised or a 3rd party WordPress API service server has been compromised where all these 15000 users account can be clients.
We will update the article, after further investigation and response from Getresponse.com security team.
45000 more wordpress has been compromised on second day of hack and Getresponse suspend the account of hacker. Read full story here.