webpack/webpack-dev-server v6.1.0 on GitHub

Run as a plugin from the top-level plugins of a multi-configuration, serving every configuration from one server. (by @alexander-akait in #5765)
Fix client progress modes, socket URL credentials, overlay and progress lifecycles, server startup error handling and local IP lookup; export BaseServer. (by @alexander-akait in #5739)
The browser client, the error overlay and both transports now come from webpack-dev-middleware, so this package has no client code of its own. Every option keeps its name and meaning, allowedHosts and the origin checks still apply here, and this server's { type } messages are still sent next to the middleware's, so React Refresh keeps working. client/index.js, client/socket.js and client/clients/WebSocketClient.js still resolve while the client's internal files are gone, and the console wording, the overlay and the progress indicator are now the middleware's. client.webSocketTransport: "sse" adds Server-Sent Events, a universal build now runs in Node without the client throwing, and sendMessage(), getClientEntry() and getClientHotEntry() still work, a subclass's overrides included, but are deprecated. (by @alexander-akait in #5750)

Keep hot and live reload working after a cancelled "Leave site?" dialog. (by @alexander-akait in #5744)
Keep the overlay for a runtime error thrown while the page is still loading. (by @alexander-akait in #5745)
Validate the Host and Origin headers and enforce same-origin checks on WebSocket upgrade requests handled by proxies with ws: true. This prevents cross-origin pages from connecting to proxied WebSocket services through the development server. (by @UlisesGascon in cb1534a)
Validate options with a precompiled schema to cut ~115ms from startup. (by @alexander-akait in #5746)
Validate Host and HTTP/2 authority headers independently of Origin protocol exceptions, including when allowedHosts is "all". Handle malformed open-editor URLs with a controlled response and parse their query without relying on the Host header. (by @bjohansebas in #5771)