“The Postal Service has addressed the issue by providing clear instructions and guidance to our employees tasked with the responsibility for handling these requests, and we will follow up with additional training,” Mr. Partenheimer’s statement said. The Postal Service said it would also change how it handles and processes requests as an additional safeguard.

Mr. Partenheimer declined to say whether the Postal Service had taken any disciplinary action in the case.

Ms. Spanberger said in an interview that she discussed the matter on Thursday afternoon with top Postal Service officials, who told her that the request somehow did not go through a standard open records request, but instead went through the human resources department. That also may explain why the request was returned so quickly.

She said it was “absolutely against the law” for the Postal Service to release the document. The Postal Service, she said, was “blaming it on one particular woman who is the one responsible for this,” an answer that she said made her “incredulous.”

The records request went to the Postal Service because Ms. Spanberger had worked in the agency’s law enforcement section before working for the C.I.A. and had to fill out a similar SF-86 document.

America Rising obtained the file in an uncharacteristically rapid fashion. Ms. Spanberger said she hired an opposition research firm in December to scour her background, a common practice by candidates. The firm filed a request through the Freedom of Information Act for her personnel information from the federal government in December, she said, and has not yet received a response.

America Rising initially filed its FOIA request on July 9 to the National Records Center, which sent it to the Postal Service on July 12. The Postal Inspection Service delivered a response to America Rising on July 30.