A single source tells Bloomberg that the department, which provides the Navy with nuclear reactors for submarines, was caught up in the zero-day vulnerability that has hit more than 50 organizations in recent days. The exploit affects on-premises versions of SharePoint, but not the SharePoint Online service that Microsoft operates as part of its Microsoft 365 cloud service.

While the nuclear weapons agency has reportedly been affected by the SharePoint exploit, no sensitive or classified information has leaked according to Bloomberg. That might be because the US Department of Energy uses Microsoft 365 cloud systems for a lot of its SharePoint work. “The department was minimally impacted due to its widespread use of the Microsoft M365 cloud and very capable cybersecurity systems,” says a Department of Energy spokesperson in a statement to Bloomberg. “A very small number of systems were impacted. All impacted systems are being restored.”

Microsoft has now patched all versions of SharePoint that are impacted by the zero-day exploit. The flaw allowed hackers to remotely access SharePoint servers and steal data, passwords, and even move across connected services. The exploit appears to have originated from a combination of two bugs that were presented at the Pwn2Own hacking contest in May.