Hello @ZDouiri,
We have ENH-000130906 logged to support Captcha in Survey123. The issue at the moment is if Survey123 were to implement Captcha it would provide a false sense of security. While automated form fills could be prevented for a public survey the REST endpoint is still publicly available for spam submissions and a basic python script would be able to spoof submissions bypassing Survey123 altogether.
Ultimately to adequately make the workflow of using Captcha effective we need the implementation of ENH-000122698 on the ArcGIS Online/Enterprise side of things to be implemented so that both the Survey form and REST endpoint can be configured to prevent spam submissions.
A few things that can be done now is to set “Only one submission is allowed per submitter” under the Collaborate > Share survey tab as that will use a browser cookie to prevent multiple submissions. Please see this documentation for the workflow.
Alternatively another workflow that could be used is to publish a Survey123 survey then take the feature service that was created and re-add it to the Organization as an item with credentials stored so that limitations can be placed on the service to limit rate/referrer usage, and then update the form to use the feature service with stored credentials. From there the survey form can be embedded into a website using the Survey123 web app JSAPI and incorporated on a page with Captcha.
Thank you,
Zach
Thank you,
Zach