This indicates an attack attempt to exploit a Security Bypass vulnerability in Oracle Java.
The vulnerability is due to insufficient sanitizing of a parameter when handling a JNLP file. A remote attacker can exploit this to bypass security checks of vulnerable systems.
JDK and JRE 7 Update 7 and earlier
JDK and JRE 6 Update 35 and earlier
JDK and JRE 5.0 Update 36 and earlier
SDK and JRE 1.4.2_38 and earlier
Security Bypass: Remote attackers can bypass security checks of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.