In a report released Monday by the Stevens Institute of Technology and Princeton University’s Electoral Innovation Lab, researchers said that missteps by the New York City Board of Elections had inadvertently allowed the lab to determine the votes of 378 New Yorkers in the mayoral primary. Those voters include the mayor’s son and a former New York City deputy mayor, Robert K. Steel.

Because that information is supposed to be secret, in accordance with state law, the report’s findings suggest a breach of one of America’s most prized guarantees, the secret ballot, and represent another blemish for the city Board of Elections.

“I am appalled by this violation of my privacy,” said Dante de Blasio, a registered Democrat, via a spokesman for his father, the mayor. “My main concern is not that people will know who I voted for, but rather that the B.O.E. has repeatedly shown complete incompetence and still hasn’t been reformed by the state. Hundreds of my fellow voters have had their right to a private ballot violated by the B.O.E.’s blatant carelessness. Enough is enough.”