code: public function onKernelResponse(FilterResponseEvent $event): void
      {
          if (!$this->scopeMatcher->isContaoMasterRequest($event)) {
              return;
          }
  
          $request = $event->getRequest();
  
          if (!$request->isMethod(Request::METHOD_GET)) {
              return;
          }
  
          $response = $event->getResponse();
  
          if (200 !== $response->getStatusCode()) {
              return;
          }
  
          $token = $this->tokenStorage->getToken();
  
          if (null === $token || $this->authenticationTrustResolver->isAnonymous($token)) {
              return;
          }
  
          if ($this->scopeMatcher->isBackendRequest($request)) {
              $this->storeBackendReferer($request);
          } else {
              $this->storeFrontendReferer($request);
          }
      }
docs: Stores the referer in the session.