Senior officials inside the national security apparatus were briefed on the documents on April 6, the same day the leak was first reported by The New York Times, according to two other senior U.S. officials. And the Biden administration began looking into the leak only last week. The delay has current and former officials asking why the breach went unnoticed for so long. And it suggests that there may be a large online blind spot in the U.S. intelligence gathering process. “Federal government agencies do not proactively monitor online forums looking for threat-related activity,” said John Cohen, the former acting...