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Re: Technique: accessible scripts...

From: Alan J. Flavell <flavell@a5.ph.gla.ac.uk>
Date: Mon, 20 Nov 2000 20:23:19 +0000 (GMT)
To: Charles McCathieNevile <charles@w3.org>
cc: WAI GL <w3c-wai-gl@w3.org>
Message-ID: <Pine.OSF.4.21-pb.0011202013500.30331-100000@a5.ph.gla.ac.uk>
On Mon, 20 Nov 2000, Charles McCathieNevile wrote:

> On the server when the page is submitted:
> 
> if (validated=="no") { valider() }
> else { reserver() }

The aim is clear: to offer a convenient and fast-acting correction of
bad input at the client side, to save the round trip to the server.
So far, so good.

But if this code means what I think it means, then (quite irrespective
of accessibility) I'm afraid there is a problem, since a malicious
user needs only to edit the source to claim that client-side
validation was done when in fact it wasn't, in order to bypass the
validation checks.

It's a firm principle that the server must _always_ validate the
inputs, no matter whether it thinks they have been pre-validated
on the client-side or not.

best regards
Received on Monday, 20 November 2000 15:23:36 GMT

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