Microsoft’s April 2026 cumulative security update for Windows 11 is causing significant disruptions for users relying on third-party backup software, triggering an MS-DEFCON level 3 advisory from security patch analyst Susan Bradley at AskWoody. The problematic update, KB5083769, applies to Windows 11 versions 24H2 and 25H2 (OS Builds 26200.8246 and 26100.8246), released on April 14, […] The post Microsoft Windows 11 April 2026 Security Update Breaks Third-Party Backup Applications appeared first on Cyber Security News.