Esbuild version 0.6.1 represents a subtle yet noteworthy update over its predecessor, version 0.6.0, in the rapidly evolving world of JavaScript bundling and minification. Both versions maintain the core promise of Esbuild: delivering exceptional speed and efficiency in the bundling process. This makes them compelling choices for developers seeking to optimize build times and reduce the size of their JavaScript applications, leading to faster load times and improved user experiences.
While the description, license (MIT), and repository details remain constant, indicating a commitment to open-source principles and ongoing development, key differences lie in the distribution metadata. Version 0.6.1 exhibits a slightly larger unpacked size (24405 bytes) compared to 0.6.0 (23659 bytes), suggesting the introduction of new features, bug fixes, or performance enhancements. The file count remains consistent at 6. The release date also marks the newer version released a few hours later than the previous version. For developers, this implies a potential for improved stability and refined functionality in 0.6.1.
Given Esbuild's focus on speed, even minor updates like this can contribute to a more streamlined development workflow. Upgrading from 0.6.0 to 0.6.1 is likely a worthwhile consideration for those who prioritize the latest optimizations and reliability improvements within this powerful bundling tool.
All the vulnerabilities related to the version 0.6.1 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.