Esbuild version 0.16.9 is a minor patch release following 0.16.8 of this extremely fast JavaScript and CSS bundler and minifier. Primarily, the differences between the two versions lie in updated dependency versions. Both versions maintain identical functionality with a focus on speed and efficiency in bundling and minifying web assets.
For developers, esbuild offers a compelling alternative to slower JavaScript bundlers. Its speed drastically reduces build times, enhancing the development experience. Key features include: blazing-fast build times, support for modern JavaScript and CSS features, tree shaking to eliminate dead code, code minification, source maps for debugging, and a simple, intuitive API. Both versions list the exact same set of architecture-specific dependencies, as optional dependencies, ensuring compatibility across a wide range of operating systems and architectures, including Linux, Windows, macOS, Android, and FreeBSD on various processor architectures (x64, arm, arm64, etc.). The "fileCount" for both versions is same, while "unpackedSize" has a very small difference of 10 bytes. This suggests that the core functionality remains unchanged, and the update likely addresses internal improvements or dependency adjustments and fixes instead of new features. Upgrading from 0.16.8 to 0.16.9 should be seamless and won't require any code changes for projects already using esbuild.
All the vulnerabilities related to the version 0.16.9 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.