Every username, password and email address used by members of the Ubuntu Forums was accessed. More than 1.82 million accounts were stolen, according to a notice posted on the forums home page Saturday night. The site was defaced before it was taken down at 2015 UTC; the home page was replaced with a logo of a penguin wielding an assault rifle. Ubuntu uses MD5 to hash passwords as per vBulletin, the software upon which the forums are built, Ars Technica reported yesterday.
Source: https://threatpost.com/ubuntu-forums-remain-down-after-password-breach/101428/