In UNDERTOW-2269, a new method was added to merge query parameters from an existing request with those provided during a forward or include.

This implementation erroneously modifies the underlying HttpServerExchange (or shared parameter map) directly. As a result, the merged parameters persist in the ServletRequest even after the include returns.

According to Section 9.1.1 of the Jakarta Servlet Specification (6.0), parameters specified in a RequestDispatcher are scoped strictly to the include or forward call and must not be visible to the calling page after the dispatch completes.

Expected Behavior: The merged parameters should be visible only to the target resource (via a Request Wrapper or scoped query map). The original exchange and the ServletRequest seen by the caller must remain unchanged.

For details see the requesting dispatching in the specification.