Cross-site scripting (XSS) vulnerability in the URLDecoder function in JRE before 1.8, as used in Apache Struts 2.x before 2.3.28, when using a single byte page encoding, allows remote attackers to inject arbitrary web script or HTML via multi-byte characters in a url-encoded parameter.
https://issues.apache.org/jira/browse/WW-4507
http://www.securitytracker.com/id/1035268