1. Go ahead and use the documents to the company’s benefit, but make clear to your boss that you don’t want him passing confidential information to you in the future. If he threatens to fire you, threaten to leak the news to the press.
2. Confront your boss privately, and let him know that you’re uncomfortable with how the documents were obtained and what possessing them says about the company’s culture. In addition to the question of the legality of using the information, point out that it is a public relations nightmare waiting to happen.
3. Talk to the company’s legal counsel, and contact the Society of Competitive Intelligence Professionals for guidance. Then, with their opinions and facts to back you up, go to your boss.

Miquel Vasquez was proud of his job as a new product manager for a biotechnology start-up, and he enjoyed the high stakes and tough decisions that went along with the job. But as he sat in his den after a long day, he was troubled, struggling over what had happened earlier that day and the information he now possessed.
Just before lunch, Miquel’s boss had handed him a stack of private strategic documents from their closest competitor. It was a competitive intelligence gold mine—product plans, pricing strategies, partnership agreements, and other documents, most clearly marked “proprietary and confidential.” When Miquel asked where the documents came from, his boss told him, with a touch of pride, that he had taken them off the competing firm’s server. “I got into a private section of their intranet and downloaded everything that looked interesting,” he said.