This issue was discussed by the Drupal Security Team, and their decision was that this can be solved in a public issue.
Problem/Motivation
When the issue was reported to the security team, @cilefen made the following observation:
> However, there are a few example files in the library, such as recaptcha-v2-checkbox-explicit.php, which contains the follow, which is basically identical to the example-captcha.php file you attached:
// The POST data here is unfiltered because this is an example.
// In production, *always* sanitise and validate your input'
?>
<h2><kbd>POST</kbd> data</h2>
<kbd><pre><?php var_export($_POST);?></pre></kbd>
Original report by @sarswatsudhakar references files in 7.x-2.2 which were later removed (https://git.drupalcode.org/project/recaptcha/-/blob/7.x-2.2/recaptcha-ph...)
> Line 76 of example-captcha.php sends unvalidated data to a web browser, which can result in the browser executing malicious code. in below mention files
Steps to reproduce
@larowlan attempted to exploit this on nginx and apache and was unable to.
Proposed resolution
From @poker10: remove the recaptcha-php/examples folder from 7.x-2.x version of the module. This is recommended so that the example code will not communicate insecure patterns.
Remaining tasks
User interface changes
API changes
Data model changes
