Incorrect order of security checks in Apache Wicket. org.apache.wicket.protocol.http.ResourceIsolationRequestCycleListener obtains the page a request targets before it consults its resource isolation policies, because those policies are passed that page. Obtaining the page instantiates it, and instantiating a page runs the configured org.apache.wicket.authorization.IAuthorizationStrategy. An application that refuses an unauthenticated visitor by throwing org.apache.wicket.RestartResponseAtInterceptPageException therefore throws it from inside the isolation listener, before any policy has run. That exception replaces the request handler, so the policies are never consulted and a request that came from another origin is not refused. The exception's constructor stores the URL of the request it interrupted, so that Component#continueToOriginalDestination() can resume it once the visitor has signed in. The stored URL is the one the policies would have refused. On sign in Wicket redirects to it, and that redirect is same-origin, so the policies allow it and the listener runs in the newly authenticated session. The whole URL is stored, its query string included, so an ordinary org.apache.wicket.markup.html.form.Form is resumed with the field values the original request carried in its query string and Form#onSubmit() runs with values another origin chose. A form POST is not needed for this; a plain top-level navigation carries them. An application is affected where it registers ResourceIsolationRequestCycleListener, which is opt-in and is not registered by default, and where it refuses unauthorized access with RestartResponseAtInterceptPageException followed by continueToOriginalDestination(). No application override is involved on that path: IAuthorizationStrategy#isInstantiationAuthorized() documents throwing that exception, org.apache.wicket.authroles.authentication.AuthenticatedWebApplication throws it and org.apache.wicket.authroles.authentication.panel.UsernamePasswordPanel continues to the original destination, and org.apache.wicket.authorization.strategies.page.SimplePageAuthorizationStrategy in wicket-core installs the same pattern. A visitor who is already signed in is not affected, because no interception occurs. Request-body parameters stored alongside the intercepted URL are not applied to the resumed form: the resumption is a redirect, so the resumed request is a GET, and form components read their values from the query string on a GET. As a workaround, refuse unauthorized access with org.apache.wicket.RestartResponseException instead, which does not store the original destination; visitors are then not returned to the page they asked for after signing in. This issue affects Apache Wicket: from 9.1.0 through 9.24.0, from 10.0.0 through 10.11.0. Releases before 9.1.0, which is every 8.x release and 9.0.0, are not affected, because the resource isolation this issue concerns was introduced in 9.1.0. They are not protected either. Their only cross-origin defence is org.apache.wicket.protocol.http.CsrfPreventionRequestCycleListener, which works out where a request came from by reading its Origin header and falling back to its Referer header. Neither header need arrive: a browser does not send Origin on the plain GET a link uses, and the document on the other origin decides through its own referrer policy whether a Referer reaches the application at all. That mechanism therefore never made the guarantee the Fetch Metadata based policy makes, and on those releases a listener invocation from another origin is not reliably refused in the first place. Anyone on a release before 9.1.0 who wants this protection should upgrade to 9.x or 10.x and register ResourceIsolationRequestCycleListener. Users are recommended to upgrade to version 9.25.0 or 10.12.0, which fix the issue.