and use their fiduciary duty as a legal basis to compel patronage of their services

Do you mean a hacker should find a company’s tech vulnerability and then either: a) inform the company that a vulnerability exists and they should pay $XYZ to learn what it is, or b) inform the company that a vulnerability is known and it will be disclosed unless $XYZ is paid, or c) simply inform the company of the vulnerability and hope that they’ll pay the hacker to consult on how to fix it?

Scenario A is generally permissible, if such a vulnerability does exist. Things like NDAs and contracts can be agreed before the hacker describes the vulnerability, to legally protect the company in case the hacker was bluffing. That said, even without contracts, falsely claiming that a vulnerability exists or that the hacker knows what it is would be fraud in most jurisdictions.

Scenario B is blackmail, and is illegal. [shocked Pikachu face]

Scenario C is possible, although there’s no guarantee that the company is looking for consulting. Although if the hacker’s speciality is both how to identify and patch such specific vulnerabilities, this may be more likely.

That said, taking a step back, are you sure you meant to reference the fiduciary duty that corporate directors owe to their shareholders? This is not the same as the business judgement rule, where directors must act with reasonable prudence in the company’s best interest. The latter rule exists because there may be multiple tactics to fully honor the fiduciary duty, and it would be inequitable to allow suits against directors just because they decided to achieve the objective in different ways.

Neither the fiduciary duty nor the business judgement rule penalize a director just because a business challenge arises, such as a data breach. Rather, the fiduciary duty is violated when a director hides info from the shareholders, or does not follow explicit instructions from the shareholders. And the business judgment rule will not protect a director that is working in bad faith or taking unreasonable risks with the company’s assets.

Declining to hire a hacker as a consultant is a reasonable course of action. It would be a strange – but not impossible – instruction for the shareholders to order the management to “never negotiate with terrorists” but absent such a command, there wouldn’t be a violation of the director’s duty of care.