Esbuild versions 0.6.33 and 0.6.34 are both iterations of the incredibly fast JavaScript bundler and minifier, designed to significantly improve build times for modern web applications. Both versions share the same MIT license, ensuring developer-friendly usage and modification. They also pull from the same GitHub repository, reflecting a continuous development process. The core functionality and description remain consistent, highlighting esbuild's primary purpose of bundling and minifying JavaScript code with exceptional speed. The unpacked size and the number of files included in the distribution are also identical between the two versions, suggesting similar overall architecture and features.
The principal difference lies in their release dates. Version 0.6.34 was released on September 11, 2020, shortly after version 0.6.33, which was released on September 9, 2020. This short gap suggests that version 0.6.34 likely contains bug fixes, minor improvements, or potentially new, smaller features implemented immediately after the previous release. For developers, this indicates that upgrading from 0.6.33 to 0.6.34 is likely a safe and recommended move to leverage the latest refinements. While the specific changes aren't explicitly described in the provided data, the rapid release cycle hints at an effort to ensure stability and optimal performance. Developers using esbuild should consider keeping up with these minor version bumps to benefit from these incremental improvements in their bundling process.
All the vulnerabilities related to the version 0.6.34 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.