CVE 2012-3388
The is_enrolled function in lib/accesslib.php in Moodle 2.2.x before 2.2.4 and 2.3.x before 2.3.1 does not properly interact with the caching feature, which might allow remote authenticated users to bypass an intended capability check via unspecified vectors that trigger caching of a user record.
See the 
CVE page on Mitre.org
for more details.
