jetty: requests to the ConcatServlet and WelcomeFilter are able to access protected resources within the WEB-INF directory

For Eclipse Jetty versions = 9.4.40, = 10.0.2, = 11.0.2, it is possible for requests to the ConcatServlet with a doubly encoded path to access protected resources within the WEB-INF directory. For example a request to /concat?/%2557EB-INF/web.xml can retrieve the web.xml file. This can reveal...