(CRM) and marketing / leads management to Company XYZ. Which of the following is the MOST important to be considered before going ahead with the service?

Internal auditor approval is a governance step that may be required procedurally, but it does not by itself ensure the third party maintains adequate security controls over sensitive data.

The ability to perform penetration testing on the external web system is a useful security assurance activity but is secondary to having contractual security obligations and audit rights in place.

Embedding security controls and audit rights directly into the contract is the most important step because it creates legally enforceable obligations on the vendor, ensures accountability for data protection, and gives the organization the ability to verify compliance - without this, there is no mechanism to enforce security standards on the third party.

A physical site audit provides a point-in-time assessment of the vendor's operations but is less comprehensive and less continuously enforceable than contractual security controls with ongoing audit rights.