Esbuild versions 0.5.6 and 0.5.7 are both iterations of the extremely fast JavaScript bundler and minifier, designed to streamline the modern web development workflow. Both versions maintain the same core description, MIT license, and repository location, indicating a focus on stability and community-driven development. The distribution details, including fileCount and unpackedSize, remain identical between the two releases. This suggests that the code base and overall structure of the package are consistent.
The primary difference lies in their release dates. Version 0.5.7 was released on 2020-06-21, approximately 12 hours after 0.5.6, released on 2020-06-20. This short interval hints that version 0.5.7 likely contains minor bug fixes, performance improvements, or very small feature additions built upon the foundation of version 0.5.6. For developers, especially those integrating esbuild into continuous integration pipelines or performance-sensitive applications, upgrading from 0.5.6 to 0.5.7 is probably advisable, but a deep dive into release notes is suggested due to the close release dates, which is standard practice when dealing with software libraries. Developers may want to closely watch the GitHub repository for precise changes between versions for specific details.
All the vulnerabilities related to the version 0.5.7 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.