If any of your users install the AdBlock Plus extension for IE, you'll find that your content gets filled with "abp" attributes.
This plugin just takes care to remove them from the CKEditor output.
It doesn't have any configuration, button, nor anything complex, you just add it your editor and it will remove those extra attributes that are inserted on each element.
Q: But doesn't the "ACF" take care of restricting the content generated by CKEditor?
A: No. The ACF only filters the input data, so when your users go and edit a nice form that they inserted one year ago it will be gone (and you'll hear their screams right from your home), but their browser can insert this kind of random garbage without any restriction.