A wide-ranging October 2025 cumulative update for Windows 11 (KB5066835), and at least one related preview package, has broken many local IIS-hosted sites and developer workflows — causing ERR_CONNECTION_RESET, ERR_HTTP2_PROTOCOL_ERROR and outright failure of localhost-based services for...
Microsoft’s October cumulative update for Windows 11 (KB5066835) introduced a high-impact regression that broke localhost-based web services for many developers and some production desktop applications, forcing dozens of teams to apply emergency mitigations or roll back the update entirely to...