The best recommendation for a risk practitioner upon learning that an employee inadvertently disclosed sensitive data to a vendor is to invoke the incident response plan. An incident responseplan is a document that defines the roles, responsibilities, procedures, and resources fordetecting, analyzing, containing, eradicating, recovering, and reporting on security incidents that could affect the organization’s IT systems or data. An incident response plan helps to protect and restore the confidentiality, integrity, and availability of the organization’s information assets, and to comply with the relevant laws, regulations, standards, and contracts. Invoking the incident response plan is the best recommendation, because it helps to respond to and mitigate the security incident, and to minimize the damage and impact of the data disclosure. Invoking the incident response plan also helps to communicate and coordinate the incident response actions and strategies with the internal and external stakeholders, such as the data owners, users, custodians, and regulators, and to report and disclose the incident as required. The other options are not as effective as invoking the incident response plan, although they may be part of or derived from the incident response plan. Enrolling the employee in additional security training, conducting an internal audit, and instructing the vendor to delete the data are all examples of corrective or preventive actions, which may help to prevent or deter the recurrence of the data disclosure, or to verify or validate the data security, but they do not necessarily address or resolve the current security incident. References = Risk and Information Systems Control Study Manual, Chapter 5, Section 5.4.1, page 5-32.