I know this is an old message, but someone may find it in a search like I did.

The CGI module spec doesn't disagree with the W3C spec for the FORM tag. They're not referring to the same thing.

In HTML, the action property of the form tag is not optional. If you want to, you can leave it as an empty string (action="") and you will still pass the validator.

In CGI's start_form() method, the action method is optional. If you don't define the action property of the start_form method, it will create a form tag with an action property that points to the current script.

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-- GhodMode