Esbuild 0.16.3 is a minor version update to the blazing-fast JavaScript and CSS bundler, building upon the previous stable release of 0.16.2. Upon inspection, the core functionality and dependency landscape remain remarkably consistent. The primary difference lies in the version numbers of the @esbuild/* platform-specific packages listed as both dependencies and optional dependencies. These packages, crucial for adapting Esbuild to diverse operating systems and architectures (Linux, Windows, macOS, Android, FreeBSD, etc., across x64, ARM, and other processor types), have been bumped from 0.16.2 to 0.16.3.
For developers, this often signifies important bug fixes, performance improvements, or compatibility adjustments tailored to specific environments. While the core API likely remains unchanged, upgrading to 0.16.3 is advisable for enhanced stability and potentially better performance, especially when targeting a wide range of deployment platforms. The unchanged fileCount and unpackedSize in the dist object suggest the underlying file structure and overall size of the package remain consistent. Most importantly, the releaseDate showcases that this is a recent update, and migrating to it ensures your build process is leveraging the latest enhancements available for this tool. Ultimately, staying updated means faster bundling times and improved compatibility for your JavaScript and CSS projects.
All the vulnerabilities related to the version 0.16.3 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.