Paul Ceglia, who claims a 2003 contract with Mark Zuckerberg made him a partner in Facebook, said the company's lawyers committed an "egregious and massive violation" of his privacy by publishing his email passwords.
Facebook's lawyers, from Gibson, Dunn & Crutcher, included passwords to Ceglia's web-based email accounts in a court document filed last week in federal court in Buffalo, New York, according to a filing by Ceglia.
The papers were removed from the public file the next day and Ceglia, in Ireland, changed the passwords, according to his lawyers.
"Counsel's baffling misconduct resulted in Ceglia's email accounts being accessible to the world for 12 hours," his lawyers said in court papers.
They said they intend to ask the court for sanctions and lawyers'fees.