they add the previous values for record fields as hidden form variables, and check if these values are still the current values at the moment of the update.
Unless combined with both encryption and digital signatures, I'd say it would generally be a security risk to pass data to the browser and rely on that they come back unaltered.

Don't hide sensitive information in hidden form fields, (searchsecurity.techtarget.com).

Update: Re-phrased "it is" to "it would generally be".

--
Andreas

In reply to Re^2: Preventing Duplicates by andreas1234567
in thread Preventing Duplicates by Anonymous Monk

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