>In the case of a work made for hire, the employer or other person for whom the work was prepared is considered the author for purposes of this title, and, unless the parties have expressly agreed otherwise in a written instrument signed by them, owns all of the rights comprised in the copyright.
https://www.copyright.gov/title17/92chap2.html#201
You are responsible for infringing works you publish, whether they are produced by commission or employee.
Due diligence refers to the reasonable care, investigation, or steps that a person or entity is expected to take before entering into a contract, transaction, or situation that carries potential risks or liabilities.
Vicarious copyright infringement is based on respondeat superior, a common law principle that holds employers legally responsible for the acts of an employee, if such acts are within the scope and nature of the employment.