Esbuild version 0.16.13 represents a minor update over its predecessor, version 0.16.12, in the rapidly evolving world of JavaScript and CSS bundlers. Both versions are built around the core premise of extreme speed and efficiency in bundling and minifying code, a compelling feature for developers seeking to optimize build times and application performance.
A notable aspect remains the consistent dependency structure: both versions rely on a comprehensive set of platform-specific binaries (e.g., @esbuild/linux-x64, @esbuild/darwin-arm64) as both dependencies and optional dependencies, ensuring esbuild can function across diverse operating systems and architectures. The specific versions of these platform-dependent packages are aligned directly with the core esbuild version, meaning 0.16.13 relies on version "0.16.13" of those platform specific packages.
The key difference between the versions relates to the release date and subtle internal improvements. Version 0.16.13 was released on January 2, 2023, a few days after version 0.16.12, released on December 28, 2022. The file sizes differ slightly and the unpacked size of 0.16.13 is a bit bigger, which suggests potential bug fixes, performance tweaks, or minor feature enhancements incorporated into the newer release. Typically, patch versions like these address stability concerns. Developers should always consult the official esbuild changelog or release notes to gain a deeper understanding of the concrete changes if migrating between versions to ensure best security and stability.
All the vulnerabilities related to the version 0.16.13 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.