Index: /trunk/src/VBox/ValidationKit/tests/additions/tdAddGuestCtrl.py
===================================================================
--- /trunk/src/VBox/ValidationKit/tests/additions/tdAddGuestCtrl.py	(revision 84655)
+++ /trunk/src/VBox/ValidationKit/tests/additions/tdAddGuestCtrl.py	(revision 84656)
@@ -3339,4 +3339,7 @@
             [ tdTestDirCreate(sDirectory = '/..' ), tdTestResultFailure() ],
             [ tdTestDirCreate(sDirectory = '/../' ), tdTestResultFailure() ],
+            # Format strings. Dangerous.
+            [ tdTestDirCreate(sDirectory = 'foo%sbar%sbaz%d' ), tdTestResultFailure() ],
+            [ tdTestDirCreate(sDirectory = '%f%%boo%%bar%RI32' ), tdTestResultFailure() ],
         ];
         if oTestVm.isWindows() or oTestVm.isOS2():