[whatwg] Allowing ">" in attribute values

Mike Shaver mike.shaver at gmail.com
Fri Jun 25 13:09:44 PDT 2010

One advantage is almost the same as your footnote: JavaScript source is
permitted in the values of many attributes, and can certainly contain the >

On Jun 25, 2010 12:34 PM, "Benjamin M. Schwartz" <bmschwar at fas.harvard.edu>
> On 06/25/2010 11:50 AM, Boris Zbarsky wrote:
>> It seems like what you want here is for browsers to parse as they do
>> now, but a particular subset of browser-accepted syntax to be enshrined
>> so that when defining your restrictions over content you control you can
>> just say "follow the spec" instead of "follow the spec and don't put '>'
>> in attribute values", right?
> That's more or less how I feel. The spec places requirements on how "user
> agents, data mining tools, and conformance checkers" must handle
> non-conforming input, but there are many other things in the world that
> process HTML. In other applications, it may be acceptable to have
> undefined behavior on non-conforming input, like in ISO C.
> HTML5 has a very clear specification of conformance, and a validator is
> widely available. If I build a tool that guarantees correct behavior only
> on conforming inputs, then users can easily check their documents for
> conformance before using my tool. If my tool has additional restrictions,
> then I need to write my own validator, and answer a lot of questions.
> I was inspired to suggest this restriction after using mod_layout for
> Apache, which inserts a banner at the top of a page. It works by doing a
> wildcard search for "<body*>". There are a number of obvious ways to
> break this [1]; one of them is by having ">" in an attribute value. I'm
> sure there are many thousands of such programs around the world.
> It sounds like most experts here would prefer to allow ">" in attribute
> values in conforming documents, and that's fine. I don't fully understand
> the advantage, but I won't argue against consensus.
> --Ben
> [1] A javascript line like "width<bodywidth && height>bodyheight" would
> also break it, as would an appropriately constructed comment. It might be
> possible to construct a regexp for this that functions correctly on all
> conformant HTML5 documents. Such a regexp would be considerably simpler
> if ">" were disallowed in attribute values.
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