[TASK] Add hint what to do when a CSRF token check failed

Resolves: #75776
Releases: master, 7.6
Change-Id: I499c8a4e87e1abda99179329b69b7cdd67f7a748
Reviewed-on: https://review.typo3.org/48372


Reviewed-by: Michael Oehlhof <typo3@oehlhof.de>
Tested-by: Michael Oehlhof <typo3@oehlhof.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/backend/Classes/Http/AjaxRequestHandler.php

@@ -197,7 +197,7 @@ class AjaxRequestHandler implements RequestHandlerInterface
         } elseif (empty($ajaxScript)) {
             $ajaxObj->setError('No backend function registered for ajaxID "' . $ajaxID . '".');
         } elseif ($csrfTokenCheck && !$this->isValidRequest($request)) {
-            $ajaxObj->setError('Invalid CSRF token detected for ajaxID "' . $ajaxID . '"!');
+            $ajaxObj->setError('Invalid CSRF token detected for ajaxID "' . $ajaxID . '", reload the backend of TYPO3');
         } else {
             $success = GeneralUtility::callUserFunction($ajaxScript, $ajaxParams, $ajaxObj, '', 1);
             if ($success === false) {