Esbuild versions 0.8.30 and 0.8.31 represent incremental updates to this extremely fast JavaScript bundler and minifier, a tool increasingly favored for its speed and efficiency in web development workflows. Both versions share the same core attributes: MIT license, repository on GitHub under the 'evanw/esbuild' project.
The key difference lies in their release dates and potentially some internal improvements. Version 0.8.31 was released on January 7, 2021, shortly after version 0.8.30, released on January 6, 2021. While both have similar unpacked sizes of around 61KB, with 0.8.31 being slightly bigger, this suggests there might be some bug fixes or minor improvements included.
For developers, this means updating from 0.8.30 to 0.8.31 likely resolves potential minor issues and incorporates the latest optimizations. Given esbuild's focus on speed, even small improvements can translate to noticeable gains in build times, especially for larger projects. As a very minimal resource consumption tool, this is very important for cloud based CI/CD. Consequently, developers adopting or maintaining esbuild should consider 0.8.31 for a potentially smoother and faster build process.
All the vulnerabilities related to the version 0.8.31 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.