Microsoft has acknowledged several significant issues arising from the Windows 11 KB5066835 update. This update, which is meant to enhance security and functionality, has inadvertently disrupted essential features for users running versions 24H2 or 25H2.
One major drawback is its impact on localhost (127.0.0.1) HTTP/2 connections, hindering the ability of locally hosted applications to connect to the network. Users are experiencing installation errors during the October 2025 Patch Tuesday update, resulting in codes such as 0x800f0922, 0x800f0983, 0x800f081f, 0x80071a2d, and 0x800f0991. To resolve these issues, Microsoft recommends downloading the patch from the Update Catalog or using the Media Creation Tool to perform an in-place upgrade.
Moreover, there is a bug affecting File Explorer’s preview pane, which incorrectly reports a security issue when attempting to preview documents. Users may encounter an error message stating that the file could harm their computer. This problem predominantly affects files downloaded from cloud services or office networks, and while uninstalling the update can restore functionality, it is not advisable.
For users experiencing issues with Logitech peripherals, certain features such as mouse shortcuts and keyboard mappings have reportedly ceased to function after the update. Additionally, problems have been reported with the Windows Recovery Environment (WinRE), where keyboards and mice become unresponsive, complicating recovery efforts for failing PCs.
To temporarily rectify issues related to localhost after the update, users can modify the Windows Registry with a PowerShell script to disable HTTP/2, thereby reverting to HTTP/1.1. The script is as follows:
New-ItemProperty -Path 'HKLM:SYSTEMCurrentControlSetServicesHTTPParameters' -Name 'EnableHttp2Tls' -PropertyType DWord -Value 0 -ForceNew-ItemProperty -Path 'HKLM:SYSTEMCurrentControlSetServicesHTTPParameters' -Name 'EnableHttp2Cleartext' -PropertyType DWord -Value 0 -ForceFurthermore, if users face issues with File Explorer’s preview pane, the temporary fix can be achieved by unblocking files through PowerShell or by modifying registry settings to disable File Explorer’s security warnings.
Microsoft is actively working on fixing these issues, but users may need to exercise patience as the patches roll out. Meanwhile, precautions such as backing up important data and performing necessary modifications can help mitigate the disruptions caused by the problematic update.