The algorithm at

http://www.whatwg.org/specs/web-apps/current-work/#constructing-the-form-data-set

does not define any special processing rules for input elements in the Submit Button state, therefore, *all* such elements will be added to the data set according to item 9: "Otherwise, append an entry to the form data set with name as the name, the value of the field element as the value, and type as the type."

However, browsers seem to work differently (at least the ones I tested - Firefox, IE, Chrome): they will append an entry to the form data set *ONLY* if the input element is a submitter, and will not do that in other cases.

There exists a rule for the button elements to exclude them from the data set if they are not submitters: item 3, sub-item 1: "The field element is a button but it is not submitter."

I suggest to add similar rule for the input elements: "The field element is an input element whose type attribute is in the Submit Button state but it is not submitter."