Esbuild version 0.0.12 is a minor update to the extremely fast JavaScript bundler and minifier, following closely on the heels of version 0.0.11. Both versions share the same core description, indicating a continued focus on speed and efficiency in JavaScript bundling. The key changes reside in the dependencies and optional dependencies. While both versions list platform-specific packages for Linux, Darwin (macOS), and Windows (64-bit), the updated version depends on esbuild-linux-64@0.0.12, esbuild-darwin-64@0.0.12, and esbuild-windows-64@0.0.12 respectively, signaling corresponding updates to the platform-specific binaries used for the bundling and minification processes.
For developers, this implies potential improvements or bug fixes within those platform-specific builds. Given the extremely rapid release cadence, these updates are likely focused on addressing immediate issues or optimizing performance further. The dist information is also useful: the unpacked size remains constant at 327 bytes, indicating that the updates are unlikely to involve significant code size changes in the core package itself. Finally the release date information tells the developer that the newer version was released shortly after the older version. Developers should review the changelogs (if available, usually found on the GitHub repository) to understand the specific nature of these platform-specific updates and assess whether they address any issues they've encountered or offer performance benefits relevant to their target platforms. These rapid iterations underscore esbuild's active development cycle and commitment to providing a cutting-edge bundling experience.
All the vulnerabilities related to the version 0.0.12 of the package
esbuild enables any website to send any requests to the development server and read the response
esbuild allows any websites to send any request to the development server and read the response due to default CORS settings.
esbuild sets Access-Control-Allow-Origin: * header to all requests, including the SSE connection, which allows any websites to send any request to the development server and read the response.
https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L121 https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L363
Attack scenario:
http://malicious.example.com).fetch('http://127.0.0.1:8000/main.js') request by JS in that malicious web page. This request is normally blocked by same-origin policy, but that's not the case for the reasons above.http://127.0.0.1:8000/main.js.In this scenario, I assumed that the attacker knows the URL of the bundle output file name. But the attacker can also get that information by
/index.html: normally you have a script tag here/assets: it's common to have a assets directory when you have JS files and CSS files in a different directory and the directory listing feature tells the attacker the list of files/esbuild SSE endpoint: the SSE endpoint sends the URL path of the changed files when the file is changed (new EventSource('/esbuild').addEventListener('change', e => console.log(e.type, e.data)))The scenario above fetches the compiled content, but if the victim has the source map option enabled, the attacker can also get the non-compiled content by fetching the source map file.
npm inpm run watchfetch('http://127.0.0.1:8000/app.js').then(r => r.text()).then(content => console.log(content)) in a different website's dev tools.Users using the serve feature may get the source code stolen by malicious websites.