The White House ordered the C.I.A. to send an unclassified email listing all employees hired by the spy agency over the last two years to comply with an executive order to shrink the federal work force, in a move that former officials say risked the list leaking to adversaries.

The list included first names and the first initial of the last name of the new hires, who are still on probation — and thus easy to dismiss. It included a large crop of young analysts and operatives who were hired specifically to focus on China, and whose identities are usually closely guarded because Chinese hackers are constantly seeking to identify them.

The agency normally would prefer not to put these names in an unclassified system. Some former officials said they worried that the list could be passed on to a team of newly hired young software experts working with Elon Musk and his government efficiency team. If that happened, the names of the employees might be more easily targeted by China, Russia or other foreign intelligence services.

One former agency officer called the reporting of the names in an unclassified email a “counterintelligence disaster.”

Current officials confirmed that the C.I.A. had sent the names of employees to the Office of Personnel Management, complying with an executive order signed by President Trump. But the officials downplayed security concerns. By sending just the first names and initials of the probationary employees, one U.S. official said, they hoped the information would be protected.

But former officials scoffed at the explanation, saying that the names and initials could be combined with other information — from driver’s license and car registration systems, social media accounts and publicly available data from universities that the agency uses as recruiting grounds — to piece together a more complete list.