A person familiar with the matter told Bloomberg News that no sensitive or classified information is known to have been compromised.

The U.S. agency responsible for maintaining and designing the nation’s cache of nuclear weapons was among those breached by a hack of Microsoft Corp.’s SharePoint document management software, according to a person with knowledge of the matter.

Microsoft has issued an alert about “active attacks” on server software used by government agencies and businesses to share documents within organizations, and recommended security updates that customers should apply immediately.

Federal cybersecurity officials have issued a warning to Microsoft users about a security flaw allowing hackers to access to certain SharePoint systems.

State CISOs in North Carolina and Arizona said their teams began work immediately to ensure on-prem SharePoint systems were secure, following the recent disclosure of an active zero-day exploit.