Esbuild version 0.4.10 represents a minor update over its predecessor, version 0.4.9. Both versions maintain the core functionality of an extremely fast JavaScript bundler and minifier, crucial for optimizing front-end web development workflows. Developers leveraging esbuild for its speed and efficiency in bundling and minifying JavaScript and TypeScript code will find both versions appealing with their MIT license and a well-maintained repository. Focusing differences between the versions, the unpacked size grew slightly from 20805 to 20806, and fileCount remains unchanged. However, the most noticeable difference lies in the release date. Version 0.4.10 was released on June 8, 2020, while version 0.4.9 was released on June 7, 2020, indicating a quick follow-up release, probably because of a bug fix. The updated version may contain crucial fixes or minor improvements. While the description and other metadata points towards a similar functionality, developers should prioritize version 0.4.10 to benefit from the freshest fixes, potential optimization and enhanced stability. Package size difference seems minor. Upgrading between these two sub-versions should thus be a straightforward and beneficial bump for most projects already using esbuild.
All the vulnerabilities related to the version 0.4.10 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.