The upstream developers have discovered a bug in the DNS lookup code of Squid, the popular WWW proxy cache. When the DNS client UDP port (assigned by the operating system at startup) is unfiltered and the network is not protected from IP spoofing, malicious users can spoof DNS lookups which could result in users being redirected to arbitrary web sites.
For the old stable distribution (woody) this problem has been fixed in version 2.4.6-2woody9.
For the stable distribution (sarge) this problem has already been fixed in version 2.5.9-9.
For the unstable distribution (sid) this problem has already been fixed in version 2.5.9-9.
We recommend that you upgrade your squid package.