CKEditor allowes <p> even if "Limit allowed HTML tags" forbids it

How it Works

1. Create an input filter that only allows the <strong> element using the Limit allowed HTML tags filter.
2. enter the text
   

   <p><strong>Test</strong></p>

   to a textfield that uses this input format.

Result:

<strong>Test</strong>

How it does not work

Now enable the CKeditor text editor on the very same input format. Do not change the Limit allowed HTML tags filter.

Result:

<p><strong>Test</strong></p>

The <p> is not longer filtered even though its not explicitly allowed.