CRLF injection vulnerability in layers_toggle.php in WebCalendar 1.0.1 might allow remote attackers to modify HTTP headers and conduct HTTP response splitting attacks via the ret parameter, which is used to redirect URL requests.
http://www.vupen.com/english/advisories/2005/2702
http://www.securityfocus.com/bid/15673
http://www.securityfocus.com/archive/1/418286/100/0/threaded
http://www.debian.org/security/2006/dsa-1002
http://vd.lwang.org/webcalendar_multiple_vulns.txt