Esbuild version 0.8.41 is a minor update to the blazing-fast JavaScript bundler and minifier, building upon the solid foundation of version 0.8.40. Both versions maintain the same core functionalities, offering developers an efficient solution for bundling and minifying their JavaScript code. They both share the same file count of 6 and unpacked size of 68676 bytes, suggesting similar content and features.
The key difference lies in the release date. Version 0.8.41 was released on February 4th, 2021, at 14:21:38 UTC, approximately ten hours after version 0.8.40, which was released on the same day at 04:18:41 UTC. This small time gap indicates that version 0.8.41 is likely a patch release addressing minor bug fixes or improvements identified shortly after the initial 0.8.40 release.
For developers considering using Esbuild, both versions offer significant advantages in build speed compared to traditional bundlers. While the core bundling and minification capabilities remain consistent between these two versions, developers should opt for the latest 0.8.41 to ensure they are benefiting from the most recent bug fixes and potentially subtle performance enhancements. Before that analyze the changelog to see if this update is relevant to specific use cases. Choosing the latest version within a stable release line provides optimal stability and reliability for your JavaScript build process, maximizing performance.
All the vulnerabilities related to the version 0.8.41 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.