Secunia's reporting a "highly critical" security flaw in Sun's JRE (Java Runtime Environment) that could allow a malicious applet to compromise your PC. The solution is to update to the following versions or later: 5.0 Update 4, 1.4.2_09, or 1.3.1_16. Yet another reason to run NoScript....

"Three unspecified vulnerabilities with the use of "reflection" APIs error may be exploited by a malicious, untrusted applet to read and write local files or execute local applications."