The class com.opensymphony.webwork.components.URL uses the method HttpServletRequest.getQueryString() which is NOT available to portlets according to the JSR-168 specification.
This was discovered while trying to get the WebWork example portlet working in uPortal 2.5.X. uPortal adds parameters to the URL prefixed by uP_ which are treated as framework parameters and not passed on to the targeted portlet via the JSR-168 APIs.
In the URL class the WebWork framework is parsing the parameters off the URL which is retrieved by the HttpServletRequest.getQueryString() method. The results of this method cannot be considered valid for a portlet according to the JSR-168 specification. One possible fix would be to use the PortletActionContext.isPortletRequest() check and only perform URL inspection if not in a portlet.