Update #KB5066835 from October 14, 2025, for Windows 11 24H2 - 25H2 and Windows Server 2025 can break IIS / localhost. Microsoft has just confirmed the bug and provided a KIR.

https://borncity.com/win/2025/10/17/windows-11-24h2-25h2-server-2025-microsoft-confirms-issue-with-iis-localhost-offers-kir-solution/