Esbuild version 0.3.4 builds upon the already impressive foundation laid by version 0.3.3, offering developers a subtly refined, yet still blazing-fast JavaScript bundling and minification experience. Both versions maintain the MIT license and originate from the same GitHub repository, reinforcing consistency for users familiar with the project. While the core functionality, described as "an extremely fast JavaScript bundler and minifier," remains consistent, subtle changes likely address bug fixes, performance improvements, or refinements to existing features.
The most noticeable difference lies in the release dates. Version 0.3.4 was released on May 18, 2020, following the release of version 0.3.3 on May 17, 2020. This short interval suggests a rapid iteration, potentially responding to issues discovered in the initial 0.3.3 release. While the fileCount and unpackedSize within the dist object remain identical, indicating no significant changes in file structure or library size, the upgrade to 0.3.4 is worthwhile for developers seeking the most stable and optimized version.
Developers should consider upgrading to leverage any potential bug fixes or performance enhancements made between the releases. Even seemingly minor version bumps can introduce improvements that contribute to a smoother development workflow and more efficient bundling process. While specific changes are undocumented within the provided metadata, the quick release of 0.3.4 signals a dedication to stability and refinement in this fast JavaScript bundler.
All the vulnerabilities related to the version 0.3.4 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.