Mac OS X firewall vulnerability was found by Synack Director of Research and well-known OS X hacker Patrick Wardle. Affected are 3.x versions of the Little Snitch firewall software released prior to build 3.6.2 running on El Capitan. Wardle will discuss the vulnerability at DEF CON next month and describe the vulnerability for the first time and describe two additional Little Snitches vulnerabilities that have been previously disclosed. Users can fix the problem simply by updating to the latest version of the firewall.
Source: https://threatpost.com/little-snitch-bug-leaves-some-mac-systems-open-to-attack/119223/