About two weeks after Mr. Bezos’ Medium post, Mr. de Becker hired FTI Consulting to do the forensic analysis of the billionaire’s iPhone. In March, Mr. de Becker said he had “high confidence” that Saudi Arabia had hacked Mr. Bezos’ phone. The FTI Consulting report that was made public this week did not offer evidence of a link between the hacking and the Enquirer story.

American Media has said that it obtained information about the affair from Ms. Sanchez’s brother, Michael Sanchez, a Hollywood talent agent whom people at The Enquirer have described as a longtime source of information and tips.

Mr. Sanchez and American Media executed a nondisclosure agreement on Oct. 18, 2018, “concerning certain information, photographs and text messages documenting an affair between Jeff Bezos and Lauren Sanchez,” according to a contract between the two parties reviewed by The New York Times.

Eight days later, Mr. Sanchez granted American Media the right to publish and license the text messages and photographs he had provided in exchange for $200,000, according to the contract and four people with knowledge of the arrangement.

“The single source of our reporting has been well documented,” American Media said in a statement. “In September of 2018, Michael Sanchez began providing all materials and information to our reporters. Any suggestion that a third party was involved in or in any way influenced our reporting is false.”

After federal agents and prosecutors examined allegations of wrongdoing by American Media in connection with the Bezos story last year, the company provided evidence showing them that Ms. Sanchez had provided text messages and compromising photos of Mr. Bezos to her brother, who passed them along to the tabloid, according to four people with knowledge of the situation.

That does not preclude the possibility that Saudi Arabia could have sent other useful information to The Enquirer. Nor were Mr. Bezos and his investigators off-base in suspecting a possible link between the tabloid and the kingdom. American Media and Saudi Arabia had both tried to build relationships with Mr. Trump, and one way to the president’s heart could have been an attack on Mr. Bezos, whom Mr. Trump once referred to as “Jeff Bozo” in a Twitter post.