IIS and localhost connections broken, DRM playback dead

The September preview update broke HTTP.sys, the kernel-mode HTTP driver that powers IIS and localhost connections. Web developers found their local development servers returning ERR_CONNECTION_RESET and ERR_HTTP2_PROTOCOL_ERROR. Production IIS websites on affected servers went down. Autodesk Vault broke. DRM-protected content — digital TV, Blu-ray and DVD playback apps — stopped working entirely. Microsoft deployed a Known Issue Rollback for enterprise, but the permanent fix didn’t arrive until October’s Patch Tuesday. Somehow, an update managed to break both web servers and movie night simultaneously.