Save button submits fields from disabled fieldsets

You can reproduce by inserting a disabled fieldset element (with some fields inside that are not disabled) either in a class sheet (like the one created by AWM) or in an administration section (code to execute):

{{html clean="false"}}
<fieldset disabled="disabled">
  <input type="text" name="test" value="shouldNotBeSubmitted" />
</fieldset>
{{/html}}

Clicking on the standard (AJAX) Save (& Continue) button shouldn't submit the fields from the disabled fieldset, but it does.