Esbuild version 0.14.50 represents a minor update over its predecessor, version 0.14.49, in the ongoing development of this extremely fast JavaScript and CSS bundler and minifier. While the core description remains the same, indicating no fundamental shift in purpose or functionality, the key difference can be found within its bundled dependencies. Both versions predictably list a comprehensive suite of platform-specific esbuild binaries as both dependencies and optional dependencies, things like esbuild-linux-64, esbuild-windows-64, and esbuild-darwin-arm64. Critically, these platform-specific binaries have been updated from version 0.14.49 to 0.14.50 across the board.
This update strategy is typical for esbuild, providing optimized native builds for various operating systems and architectures. The update to the dependencies is mostly linked to bug fixes, performance improvements, and better cross-platform compatibility in the esbuild binary for each supported system. Developers choosing between versions should prioritize 0.14.50 for the latest bug fixes and potential optimizations within the core bundling and minification process therefore leveraging most recent improvements in speed and reliability across different deployment environments. The release date difference, approximately two weeks, further solidifies 0.14.50 as the preferred choice for developers aiming to utilize the most current and refined iteration of the esbuild tool.
All the vulnerabilities related to the version 0.14.50 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.