The esbuild package's initial version, 0.0.0, released on November 26, 2017, marks the very beginning of what would become a popular JavaScript bundler and compiler. Described simply with an empty string and an ISC license, this foundational release laid the groundwork for Evan Wallace's ambitious project. Examining this initial release in contrast to a non-existent "previous stable version" (undefined) is somewhat speculative, as it represents the very starting point. It's crucial to understand this wasn't a fully functional, production-ready tool at this stage.
From a developer's perspective, version 0.0.0 offered the tantalizing glimpse of a future bundling solution. It signaled the intent to create a fast, efficient tool, but lacked the features and stability that would later define esbuild. Developers looking back might find historical interest in exploring the initial codebase, understanding the fundamental design choices that shaped the tool. It is less about using the 0.0.0 version and more about tracing evolution. For practical projects, developers should focus on stable, well-documented releases of esbuild offering robust functionalities, optimizations, and community support. The initial commit serves as a fascinating artifact for those interested in the journey of software development.
All the vulnerabilities related to the version 0.0.0 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.