CVE 2008-5184
The web interface (cgi-bin/admin.c) in CUPS before 1.3.8 uses the guest username when a user is not logged on to the web server, which makes it easier for remote attackers to bypass intended policy and conduct CSRF attacks via the (1) add and (2) cancel RSS subscription functions.
See the 
CVE page on Mitre.org
for more details.
