do not allow access to anonymised forms from frontoffice (#4665)

wcs/forms/root.py

@@ -1154,6 +1154,11 @@ class RootDirectory(AccessControlled, Directory):
 class PublicFormStatusPage(FormStatusPage):
     _q_exports = ['', 'download', 'status', 'wfedit']
 
+    def __init__(self, *args, **kwargs):
+        FormStatusPage.__init__(self, *args, **kwargs)
+        if self.filled.anonymised:
+            raise errors.TraversalError()
+
     def status(self):
         return redirect('%sbackoffice/%s/%s/' % (
                     get_publisher().get_root_url(),