Esbuild 0.18.5 is a minor version update to the blazing-fast JavaScript and CSS bundler, building upon the solid foundation established by version 0.18.4. Both versions share the same core functionality, aimed at dramatically speeding up the build process for web applications. Key benefits for developers include significantly reduced build times compared to other bundlers like Webpack and Parcel, efficient minification, and support for modern JavaScript features.
The primary difference between the two versions lies in the update of the embedded platform-specific binaries. Esbuild relies on pre-built binaries for various operating systems and architectures to achieve its exceptional performance. Version 0.18.5 includes updated versions of packages like @esbuild/linux-x64, @esbuild/win32-arm64, and @esbuild/darwin-arm64 , just to name a few, all bumped from version 0.18.4 to 0.18.5. These updates likely incorporate bug fixes and performance improvements specific to those platforms, ensuring a smoother and more reliable experience.
For developers, this means that upgrading to 0.18.5 ensures they're running the most optimized version of esbuild for their target environment. While the core API and bundling logic remain consistent, this maintenance release provides potentially tangible gains in stability and performance. Therefore, upgrading is highly recommended to leverage these refined improvements. Both versions are licensed under the MIT license and are available through npm, making them easily accessible for use in a wide range of projects.
All the vulnerabilities related to the version 0.18.5 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.