While trying to e-mail her manager, an employee has e-mailed a list of all the...

The first stage in the incident response plan under the General Data Protection Regulation (GDPR) for this scenario would be to contain the impact of the breach. This means taking immediate action to stop the unauthorized access or disclosure of personal data, and to prevent it from happening again in the future. This could involve revoking access to the data, notifying the employee who mistakenly sent the data, and implementing security measures to prevent similar breaches from occurring in the future.