Esbuild 0.19.1 is a patch release, building upon the foundation laid by version 0.19.0. Both versions serve as extremely fast JavaScript and CSS bundlers and minifiers, designed to significantly enhance build performance for web development projects. A key characteristic of both versions is their extensive support for various platforms and architectures, evident in the comprehensive list of dependencies and optional dependencies like @esbuild/linux-arm, @esbuild/win32-x64, and @esbuild/darwin-arm64, ensuring compatibility across different operating systems and CPU architectures including Linux, Windows, macOS, Android, and others. This broad support empowers developers to seamlessly integrate esbuild into their cross-platform workflows.
The core functionality remains consistent: expect rapid bundling and minification, leading to faster build times. For developers already using 0.19.0, upgrading to 0.19.1 likely involves minimal changes, focusing on potential bug fixes or minor performance improvements beneath the surface. The slight increase in unpackedSize from 131240 to 131511 bytes in the newer version hints at these subtle internal alterations. While the specific nature of enhancements is not revealed with the previous data, such patch releases commonly address identified issues or optimize existing features for increased stability and performance. Developers should consult the official esbuild changelog or release notes associated with version 0.19.1 for detailed insights.
All the vulnerabilities related to the version 0.19.1 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.