It was discovered that F*EX, a web service for transferring very large files, is not properly validating authentication IDs. While the service properly validates existing authentication IDs, an attacker who is not specifying any authentication ID at all can bypass the authentication procedure.
The oldstable distribution (lenny) does not include fex.
For the stable distribution (squeeze), this problem has been fixed in version 20100208+debian1-1+squeeze1.
For the testing distribution (wheezy), this problem will be fixed soon.
For the unstable distribution (sid), this problem has been fixed in version 20110610-1.
We recommend that you upgrade your fex packages.