Microsoft’s latest Windows 11 update has caused problems for developers, breaking the ability of users to access web applications running on their own machines. The October 2025 cumulative update (KB5066835) seems to have severed Windows’ ability to communicate with itself, resulting in HTTP/2 protocol errors and failed connections. To fix the issue, some users have found that uninstalling the update or disabling HTTP/2 in the registry works, although Microsoft has yet to acknowledge the problem. The company’s transition to Windows 11 has not been smooth, with issues affecting users’ ability to upgrade and other problems with its media creation tool and end-of-support deadlines for Office 2019 and server products.
Source: https://www.theregister.com/2025/10/16/windows_11_update_localhost