Warning: Windows Update October 2025 causes “localhost” failure
The current Windows 11 Update KB5066835 (October 2025) causes many systems to lose access to local web applications via “localhost.” Affected components include IIS and IIS Express – launching local development environments fails with errors such as ERR_CONNECTION_RESET or ERR_HTTP2_PROTOCOL_ERROR.
Recommendation:
The update should not be installed at this time, as it causes severe disruptions in local development operations.
More information and affected systems can be found here:
