In addition to a number of bug fixes and small improvements, security vulnerabilities have been discovered and fixed. As always, we recommend that you upgrade your sites to these latest versions as soon as possible. All admins of registered Moodle sites have been notified with security issue details.
Note that the 2.1 and 1.9 branches are now supported for security fixes only.
Also note that no release has been made in the 1.9 branch as there have been no serious security issues in this branch.