Esbuild 0.16.2 is a minor version update to the extremely fast JavaScript and CSS bundler and minifier, building upon version 0.16.1. At its core, both versions maintain the same fundamental purpose: efficiently bundling and minifying code for optimized web performance. The key difference lies in the dependency versions of platform-specific binaries. Both the dependencies and optionalDependencies sections for 0.16.2 show updates across all the @esbuild/* packages, moving from version 0.16.1 to 0.16.2. This means that the core esbuild package is now compatible with the new binaries for each platform. This addresses potential bugs, performance improvements, or newly supported features tailored to each specific operating system and architecture.
For developers, the upgrade to 0.16.2 is recommended as it brings along with it architecture and OS compatibility updates, ensuring smoother operation and potentially enhanced performance across a range of platforms. While the core API likely remains unchanged, this update focuses on providing a more robust and refined experience beneath the surface. The release date for version 0.16.2 is December 8, 2022, a day after the 0.16.1 release, implying the 0.16.2 had substantial underlying changes and improvements. The unpacked size is slightly different being 122899 for version 0.16.2 and 122784 for version 0.16.1. Always refer to the official esbuild documentation and release notes for a comprehensive understanding of changes and potential upgrade considerations as part of adopting the new version.
All the vulnerabilities related to the version 0.16.2 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.