Esbuild version 0.14.51 is a minor update to the extremely fast JavaScript and CSS bundler, following closely after version 0.14.50. Both versions share the same core functionality of providing blazing-fast bundling and minification, catering to developers who prioritize speed and efficiency in their build processes. The update introduces no changes to the core API, and the description and license remain identical.
However, a key difference lies in the underlying platform-specific binaries. Both versions depend on and optionally depend on the same set of platform-specific packages such as esbuild-linux-64, esbuild-darwin-arm64 and others. In the newer version all of then are version 0.14.51, reflecting the update to the core package. Version 0.14.50 includes corresponding dependencies and optional dependencies at version 0.14.50.
The changes most likely encompass bug fixes, performance improvements, and compatibility adjustments within those platform-specific binaries. While the API remains stable, upgrading from 0.14.50 to 0.14.51 ensures developers are utilizing the most recent refinements and benefit from potential enhancements to bundling speed, minification accuracy, or platform support. Also unpacked size increased from 118546 to 119021 bytes. The release date of the latest version is July 28, 2022 and the previous version was released on July 25, 2022 meaning a very short time between releases. Choosing the latest version provides access to these under-the-hood improvements without requiring any code modifications.
All the vulnerabilities related to the version 0.14.51 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.