Code:
      Ext.onReady(function(){
          Ext.create('Ext.form.field.Checkbox', {
            renderTo: Ext.getBody(),
            clearCls: '',
            boxLabel: 'Click me',
            margin: 20,
            listeners: {
              blur: { fn: function(){console.info('blur');}}
            }
          }).focus(true,true);
      });
BROWSER: GOOGLE CHROME (firefox - ok)

When I try checked field - fire event blur. Why?