We have discovered and fixed a vulnerability in our fork of WebWork. Attackers can use this vulnerability to execute Java code of their choice on systems that use this framework. The attacker needs to have an account and be able to access the Confluence web interface.
All versions of Confluence up to and including 5.6 are affected by this vulnerability.
The vulnerability has been fixed in releases 5.5.7 and 5.6.6.
For additional details see the full advisory.