Cross-site scripting (XSS) vulnerability in Serendipity before 1.5.4, when "Remember me" logins are enabled, allows remote attackers to inject arbitrary web script or HTML via unspecified vectors.
http://www.openwall.com/lists/oss-security/2010/08/31/5
http://www.openwall.com/lists/oss-security/2010/08/29/3
http://blog.s9y.org/archives/223-Serendipity-1.5.4-released.html