The US agency responsible for the nation’s nuclear arsenal, the National Nuclear Security Administration, fell victim to a sophisticated cyberattack. Exploiting zero-day vulnerabilities in Microsoft SharePoint, Chinese state-sponsored hackers infiltrated government systems, including critical US defense infrastructure. Despite officials’ assurances that no classified nuclear data was accessed, the breach highlights vulnerabilities in on-premises infrastructure management. The attack, attributed to groups like Linen Typhoon, involved stealing authentication credentials to gain unauthorized access. While the Energy Department’s adoption of cloud services minimized the impact, the breach extended to other government systems worldwide. This incident underscores the persistent threat to critical infrastructure, recalling past breaches like the 2020 SolarWinds attack. Although sensitive networks remain isolated, experts warn of potential risks, including social engineering attacks.