A significant security weakness in Microsoft SharePoint Server has been utilized in an “ongoing, extensive” exploitation initiative. The zero-day vulnerability, identified as CVE-2025-53770 (CVSS rating: 9.8), has been characterized as a derivative of CVE-2025-49706 (CVSS rating: 6.3), a deception issue in Microsoft SharePoint Server that was resolved by the technology leader during its Patch Tuesday in July 2025.