It has been discovered that in ProFTPd, an FTP server, an attacker on the same physical host as the server may be able to perform a symlink attack allowing to elevate privileges in some configurations.
For the stable distribution (squeeze), this problem has been fixed in version 1.3.3a-6squeeze6.
For the testing distribution (wheezy), this problem will be fixed soon.
For the unstable distribution (sid), this problem has been fixed in version 1.3.4a-3.
We recommend that you upgrade your proftpd-dfsg packages.