Full story here:
http://news.softpedia.com/news/An-Old-Ubuntu-Bug-Lets-Malicious-Users-Gain-Sudo-Access-479625.shtml
http://news.softpedia.com/news/An-Old-Ubuntu-Bug-Lets-Malicious-Users-Gain-Sudo-Access-479625.shtml
It appears that there's a bug in Ubuntu distributions which lets malicious users locally exploit sudo and gain access to the user's account without knowing their password. The bug was submitted to Canonical's Launchpad back in September 2013 by user Mark Smith.