Sun SDK and Java Runtime Environment (JRE) 1.4.2 through 1.4.2_04, 1.4.1 through 1.4.1_07, and 1.4.0 through 1.4.0_04 allows untrusted applets and unprivileged servlets to gain privileges and read data from other applets via unspecified vectors related to classes in the XSLT processor, aka "XML sniffing."

More... (http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2004-2764)