Moodle Permissions Privileges and Access Controls Vulnerability - CVE-2011-4584
The MNET authentication functionality in Moodle 1.9.x before 1.9.15 2.0.x before 2.0.6 and 2.1.x before 2.1.3 allows remote authenticated users to impersonate other user accounts by using the Login As feature in conjunction with a remote MNET single sign-on capability as demonstrated by a Mahara site.