This release reverts the breaking change introduced in 2.4.0 (https://github.com/socketio/socket.io/commit/f78a575f66ab693c3ea96ea88429ddb1a44c86c7).

If you are using Socket.IO v2, you should explicitly allow/disallow cross-origin requests:

• without CORS (server and client are served from the same domain):

const io = require("socket.io")(httpServer, {
  allowRequest: (req, callback) => {
    callback(null, req.headers.origin === undefined); // cross-origin requests will not be allowed
  }
});

• with CORS (server and client are served from distinct domains):

io.origins(["http://localhost:3000"]); // for local development
io.origins(["https://example.com"]);

In any case, please consider upgrading to Socket.IO v3, where this security issue is now fixed (CORS is disabled by default).

Reverts

• fix(security): do not allow all origins by default (a169050)

Links:

• Diff: https://github.com/socketio/socket.io/compare/2.4.0...2.4.1
• Client release: -
• engine.io version: ~3.5.0
• ws version: ~7.4.2