Media companies, worried that some of their most closely guarded Hollywood secrets could be exposed, are rallying to fight a proposed change to corporate-disclosure rules. The proposed regulation, under consideration by the Securities and Exchange Commission, would require a corporation to publish the salary details of as many as three nonexecutive employees whose total compensation exceeds that of any of its top five officers. Companies currently have to disclose only the pay of the chief executive officer and the next four highest-paid officers. The new rule, which the SEC is expected to decide on later this year, would apply to...