OSSEC 2.8.1 was released on September 9, 2014
OSSEC can be downloaded here. In terms of features OSSEC 2.8.1 is the same as OSSEC 2.8 except that 2.8.1 includes a fix for CVE-2014-5284 vulnerability, which allows for root escalation via temp files. Go to OSSEC GitHub repository for more information regarding this issue.
For a complete release history since 2.7, see What's New in OSSEC documentation.