Microsoft has confirmed on October 18, 2025, that the recent Windows 11 security update, KB5066835, is causing several issues for users. The problems include broken localhost HTTP/2 connections, preventing locally hosted apps from connecting to the network. Additionally, users have reported installation failures for the October 2025 Patch Tuesday update with various error codes, a bug blocking File Explorer document previews due to a false security issue, and problems with some Logitech peripherals. This mandatory security update for Windows 11 versions 24H2 and 25H2 was intended to introduce features like a movable on-screen volume indicator and faster File Explorer context menu loading. The confirmation of these issues follows user reports and requires attention from Microsoft to provide a fix. There is no information available regarding the market reaction to this specific technical issue.