See: http://lwn.net/Alerts/179585/ or: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-1711 But this link doesn't work (yet?).
Thanks, I've added the hotfix (http://plone.org/products/plonehotfix20060410) and requested builds for devel, FC-5 and FC-4.