Esbuild version 0.6.2, released on July 12, 2020, builds upon the solid foundation of its predecessor, version 0.6.1, released just a day prior. Both versions maintain the core functionality of being an incredibly fast JavaScript bundler and minifier, licensed under the MIT license and accessible through the same GitHub repository. However, subtle yet potentially significant differences exist for developers considering upgrading.
The most notable change lies in the increased unpacked size of version 0.6.2, which sits at 25029 bytes compared to version 0.6.1's 24405 bytes. Although the file count remains consistent at 6, this size difference suggests the introduction of new features, bug fixes, or performance optimizations within the newer release. Developers should investigate the changelog or release notes accompanying version 0.6.2 to understand precisely what contributes to this size increase and determine its relevance to their specific use case.
Given the minimal time separating the releases, the upgrade from 0.6.1 to 0.6.2 likely addresses critical issues or provides minor enhancements, making it a worthwhile consideration for developers seeking the most stable and optimized experience. If facing any bugs on 0.6.1, version 0.6.2 is the recommended one. Esbuild's primary selling point remains its speed, making it a compelling choice for projects where build times are paramount.
All the vulnerabilities related to the version 0.6.2 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.