The FBI raid at Mar-a-Lago last month recovered a document describing the military defenses—including nuclear capabilities—of a foreign government, according to sources who spoke to the Washington Post. The sources did not name the government. The Post previously reported that agents were specifically looking for documents related to nuclear weapons when they searched Trump's private residence in Florida, a claim Trump decried as a "hoax." According to the sources, some of the documents recovered during the raid required more than just top-secret clearance in order to be accessed.
Essentially, the documents were kept even from many senior national security officials, and only the president and some Cabinet members or officials near Cabinet level would be allowed to authorize other officials to view them on a need-to-know basis. The documents have to do with special-access programs that just a few dozen government personnel may be authorized to know about at any given time, and documents related to such programs are typically kept in a secure facility, under lock and key, with a control officer keeping an eye on them. In response to the news, a Trump lawyer decried the ongoing leaks about the case. See the full piece at the Post. (More Donald Trump stories.)