ProFTPD has updated its popular open source file transfer application to close a zero-day bug that hackers used to attack the developers' own website and plant a backdoored version of the software late last month.
Version 1.3.3d of ProFTPD plugs a critical flaw in the SQL module of the FTP software package. The buffer overflow-related bug was first reported in hacker magazine Phrack, but escaped the immediate attention of developers if not those of criminal hackers.
Unknown miscreants used the security loophole to break into the project's main servers before planting hostile code that established a backdoor into installed systems. It's unclear how many users downloaded the malign code, which was available for ProFTPD website and mirrors between 28 November and 1 December.
The latest version of the software also includes fixes for other less serious bugs, stability tweaks and other improvements, as explained in release notes here. Developers also released an "almost ready" version of the next version of the software, 1.3.4rc1. ®