W3C home > Mailing lists > Public > wai-xtech@w3.org > July 2007

Re: reCAPTCHA implementation problems

From: Ben Maurer <bmaurer@andrew.cmu.edu>
Date: Mon, 16 Jul 2007 11:08:48 -0700 (PDT)
To: Gez Lemon <gez.lemon@gmail.com>
cc: Al Gilman <Alfred.S.Gilman@ieee.org>, wai-xtech@w3.org, Colin McMillen <mcmillen@cs.cmu.edu>
Message-ID: <Pine.LNX.4.64-044.0707161102080.25097@unix32.andrew.cmu.edu>


On Mon, 16 Jul 2007, Gez Lemon wrote:

> Hi Ben,
> On 16/07/07, Ben Maurer <bmaurer@andrew.cmu.edu> wrote:
> <quote>
> Well, if they disable images, they're screwed with CAPTCHAs anyways --
> they won't be able to see the images. A blind, dialup user trying to save
> bandwidth would still be able to use the CAPTCHA because they'd see the
> psudo-alt text.
> </quote>
> Not at all. Presumably, the CAPTCHA won't have alt text, or any robot
> would be able to answer it. People who deliberately disable all images
> can enable any image they like, providing they know it's there - so
> would choose to display the CAPTCHA image to solve it.

THe CAPTCHA will have alt text that describes what it is ("This is a 
visual challenge....")

> The technique you described used CSS for a functional link ("get a new
> challenge"). If the text is moved off the screen and replaced with an
> image, someone with CSS enabled but images disabled would have no idea
> that there was text there that has been removed. You asked if there
> were any issues with that approach, and that is an issue.

Thanks for pointing out this corner case.

Received on Monday, 16 July 2007 18:08:52 UTC

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