This is a bugfix for 4.0 branch, the update is available automatically via the upgrade tool in the application. See the detailed changelog below. Among other, it fixes a potential security issue that could allow someone logged to get access to unauthorized .txt files on the server. The upgrade is of course HIGHLY recommended.
Please refer to the AjaXplorer 4.0 release if you are installing for the first time or want to upgrade from 3.2.4.