This is my proposed fix to the text filter (line 3920):

text: function( elem ) {
			// IE6 and 7 will map elem.type to 'text' for new HTML5 types (search, etc) 
			// use getAttribute instead to test this case
			return "text" === elem.getAttribute( 'type' ) || elem.getAttribute( 'type' ) === undefined;
		}

Although this is a relatively minor fix, in my opinion this is a case of invalid input = invalid output. If people wish to use input elements correctly a valid type should definitely be specified.

While I agree that specifying the type is best-practice, it is not invalid to not list it. In fact, the HTML spec doesn't define the type attribute as required, only that type defaults to "text" (something that jQuery relies on for newer HTML5 types in older browsers).

The problem is that the W3C specifies that if the type is not understood by the browser then it defaults to text. So if you have <input type="number" /> it will have a type *property* of number in HTML5-aware browsers but text in non-HTML5 browsers like IE8 or Firefox 3.

There is a fix going into 1.5.2 that will address the specific issue here, but I still think that explicitly specifying a type *attribute* is strongly recommended.

Duplicate of #8380.