Yahoo email accounts have been hacked. There has been a malicious email sent to their inboxes and after they click on it their accounts are compromised. Approximately 400 million Yahoo users are at risk. This attack was, allegedly, carried out by one person by the name of Shahin Ramezany. This person has tweeted that he/she will reveal his/her methods completely, but only after Yahoo plugs the security hole. Change your password immediately Yahoo users.