Hello. I found a bug at mod.php at Typo 3 ver. 6.1.1.

Symptom¶

For each selection of a menu at left hand side menu (e.g. "View"),
the iframe at the right hand side is refreshed and the onunload() event is
raised, and Ext.EventManager._unload() should be executed correspondingly.

However, depending on timing, onunload() is not defined and
an uncaught exception is raised instead. The error message is
as follows in Firefox 21:

TypeError: Ext.EventManager is undefined
  …unload();h(k,g,G._unload)}};…..                           ext-ba…312e.js

I think the problem is that a user can click a menu before ext-all.js is loaded,
because an external script (script tag of ext-all.js in line 43 of mod.php)
makes the browser triggers an unload event in the partial page constructed up to that point.

How to reproduce the error¶

You can reproduce the error for the following steps:

1. Get log in TYPO3 site

2. Click “Configuration” link in left side menu in /typo3/backend.php page

3. Click “Log” link in left side menu

This bug is timing-dependent.
To observe the error in high probability,
you should make step 2 and step 3 quickly.