Esbuild 0.16.1 is a minor release following closely on the heels of version 0.16.0, both of which are extremely fast JavaScript and CSS bundlers and minifiers designed to significantly improve build times. While the core functionality remains the same, the key difference lies in the dependency versions. Both versions include platform-specific binaries as dependencies and optional dependencies, enabling esbuild to run efficiently across a wide range of operating systems and architectures, including Linux, Windows, macOS, Android, and FreeBSD, supporting architectures like x64, ARM, ARM64, and others. These embedded binaries eliminate the need for external dependencies in most environments.
The update from 0.16.0 to 0.16.1 involves bumping the versions of these platform-specific dependencies. Specifically, all @esbuild/* packages see a version increment from 0.16.0 to 0.16.1. For developers, this typically translates to bug fixes and potential performance enhancements within the esbuild binaries tailored to each platform. While the surface-level API and usage remain unchanged, upgrading to 0.16.1 ensures leveraging the latest optimizations and patches made to the underlying platform-specific executables. Given the rapid release cycle, it’s recommended to check esbuild's official release notes for detailed information on the specific fixes and improvements included in the 0.16.1 update, although patch releases frequently focus on small bug fixes and stability improvements. Both versions retain the MIT license and point to the same Git repository.
All the vulnerabilities related to the version 0.16.1 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.