I known it's on the newspage as well, but some forum users might not read the newspage.
The XBOX Dashboard is what appears when you turn the XBOX on without a disc in the DVD drive. It will let you adjust system settings, manage your save games, play and rip audio CDs and configure your XBOX Live account. It is the heart of the XBOX and its most vulnerable point, because it lacks several security restrictions which are enforced on games. This includes the lack of the reboot-on-eject-button "feature", which is obligatory for all games.
The existance of an exploitable vulnerability within the dashboard could totally compromises the XBOX security system. It will make the box independent from Microsoft signed code and therefore this information is released to the public now on the 4th of July 2003, the day of the XBOX Independence.
Microsoft knows that a vulnerability within the XBOX dashboard could have serious impact. This is underlined by the fact that the dashboard checks most of its files against an internal stored SHA1 hash value before it uses them.
For an unknown reason this check is not performed on the audio (.wav) and font (.xtf) files. Unfourtunately for Microsoft there exists an exploitable integer underflow vulnerabilitiy within the font file loader which can be exploited with a malformed font file.
Find the .tgz file in the source mentioned above.