After the recent Windows 11 update KB5066835, many developers found their local web servers — including IIS, IIS Express, and Kestrel — suddenly failing to load. Browsers began throwing ERR_CONNECTION ...
Microsoft has fixed a known issue breaking HTTP/2 localhost (127.0.0.1) connections and IIS websites after installing recent Windows security updates. This bug affects both Windows 11 and Windows ...
Update 10/17/25: Microsoft fixes the bug using a KIR (Known Issue Rollback) update. More information added to end of story. Microsoft's October Windows 11 updates have broken the "localhost" ...
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