The Trump administration scrambled to minimize fallout Thursday after exposing personal information, including Social Security numbers, of hundreds of congressional staff members, intelligence researchers and even an ambassador when releasing files pertaining to the death of President John F. Kennedy.

The exposure of personal details, as well as long-guarded secrets about Cold War spycraft, came as a result of the National Archives uploading 64,000 pages of documents related — some very tangentially — to Kennedy’s 1963 assassination.

White House officials acknowledged Thursday that it was only after the papers were made public that they began combing through them for exposed details.

On Wednesday, the White House ordered that the pages be combed for exposed Social Security numbers, and officials directed the Social Security Administration to issue new numbers to the affected people, according to a senior administration official, in an extraordinary response to mitigate the potential harm of the leaks. They will also be offered free credit monitoring.

Normally, personal information like names, Social Security numbers and home addresses are scrubbed from declassified files.

William A. Harnage, a former government contractor, learned from a reporter that the White House had leaked his personal information in a file from 1977. “I consider it almost criminal,” said Harnage, 71.

In fact, the exposure could have violated U.S. privacy law, according to Mark S. Zaid, a national security lawyer and outspoken critic of President Donald Trump who has also pushed for the release of the Kennedy documents. But whether the people affected could sue for damages depended on several technicalities, he said, including the storage systems used for the data.

“The bottom line is that Social Security numbers are among the most prized data that the U.S. government seeks to protect,” Zaid said. “It is an egregious breach.”

Trump’s eagerness to make the files public without redactions, fulfilling a promise he has made since his first campaign, caused the private information to be exposed. Even as his supporters praised the release as government transparency at its finest, the administration has hastily tried to explain and remedy the situation.

“President Trump delivered on his promise of maximum transparency,” White House press secretary Karoline Leavitt said in an email, adding, “At the request of the White House, the National Archives and the Social Security Administration immediately put together an action plan to proactively help individuals whose personal information was released in the files.”

The exposed data left officials rushing to deal with the potentially serious consequences, demonstrating the challenges caused when Trump makes abrupt policy moves.

His national security team was stunned and forced to scramble after the president announced Monday that he would release the Kennedy documents with only 24 hours’ notice. Administration officials had been working to make the records public since January, when Trump signed an executive order mandating it.

But that process was still underway Monday afternoon when Trump, during a visit to the John F. Kennedy Center for the Performing Arts, said the files would be made available the next day. By Tuesday evening, some of the country’s top national security officials had spent hours trying to assess any possible hazards.

Administration officials knew before the documents went out that releasing them without redactions would expose some personal information, according to one person with knowledge of the effort who was granted anonymity to discuss the deliberations.

Tulsi Gabbard, the director of National Intelligence, championed the untouched pages. “President Trump is ushering in a new era of maximum transparency,” she wrote in a post on the social platform X on Tuesday, adding, “Promises made, promises kept.”

Despite the limited number of redactions, nothing found in the papers so far has pointed to a second gunman or other conspiracy theories about Kennedy’s 1963 assassination. Any new information was largely related to the CIA’s clandestine Cold War operations, including spying on erstwhile allies.

A former lawyer for the Trump campaign, Joseph diGenova, 80, was among the people whose personal data was revealed to the public, according to The Washington Post. “It’s absolutely outrageous,” diGenova, a frequent and ardent supporter of the president, told the newspaper, adding, “It’s like a first-grade, elementary-level rule of security to redact things like that.”

Trump himself has expressed little interest in the contents of the Kennedy files, telling The New York Times in September 2021 that he was “not that curious” about the papers. He released a larger trove of Kennedy-related documents during his first term, though he relented to intelligence officials and allowed redactions — something he would later express regret for doing.

Judy K. Barga, who supports the president, nonetheless said the leak of her personal data is “not good for anybody.” Barga, 80, is a former government contractor whose Social Security number was exposed.

“People’s private information should be kept private,” she said.