Why you should patch your Java Runtime Environment
Security restrictions could be compromised in earlier versions of JDK and JRE 6, says vendor Sun.
Secunia says, "The security issue is caused due to the JRE processing external XML entity references even though the 'external general entities' property is set to FALSE. This can be exploited to e.g. access certain URLs or cause a DoS (denial of service) via malicious XML documents."
Sun says that the JDK and JRE 6 Update 4 for multiple platforms is available for download.