TL;DR

Mock Service Worker now includes a finalize API for handler cleanup, resolving potential memory leaks and improving stability when using network interception (HTTP request mocking).

Fixes Worth Knowing

Resolved several WebSocket (real-time communication) related memory leaks, specifically when connections close or network requests are handled. These fixes prevent event listeners from accumulating and improve long-running application performance.

TL;DR

MSW now includes a critical security update, patching a vulnerability in a dependency to protect against potential regex denial-of-service attacks.

Breaking

• path-to-regexp dependency updated (may impact custom route handlers).

Fixes Worth Knowing

• Security vulnerability fixed (prevents potential DoS attacks).

Before You Upgrade

• Review any custom route handlers that directly utilize the path-to-regexp library to ensure continued compatibility.

TL;DR

Mock Service Worker now uses the standard EventTarget (web API for event handling) event emitter, improving compatibility and potentially performance with existing web platform tools.

Breaking

• EventEmitter usage is removed (requires updating code that directly interacts with MSW’s event emitter).

Fixes Worth Knowing

• Resolved an issue with event emission, improving reliability when integrating with other libraries.

Before You Upgrade

• If you directly accessed or extended the EventEmitter instance on the msw object, update your code to use standard browser events instead.