Esbuild version 0.17.9 is a patch release following closely on the heels of version 0.17.8, both maintaining the core functionality of an extremely fast JavaScript and CSS bundler and minifier. Examining the package data reveals that the primary difference between these two versions lies in the version numbers of their dependencies. All platform-specific binaries like @esbuild/linux-x64, @esbuild/darwin-arm64, and others are updated from version 0.17.8 to 0.17.9, reflecting the minor version bump in the main package. This suggests that the update likely includes bug fixes, performance improvements, or minor adjustments within these platform-specific builds, ensuring consistent behavior across different operating systems and architectures.
For developers using esbuild, this means that upgrading from 0.17.8 to 0.17.9 should be a straightforward process, requiring minimal code changes. The dependencies and optional dependencies for various platforms have been updated accordingly. The core APIs and functionalities are expected to remain the same, guaranteeing a seamless transition and continued support for streamlined builds. The update assures continued compatibility and access to the latest refinements within the esbuild ecosystem, contributing to a more robust and optimized bundling process for web development projects. Considering the library's MIT license, developers have the freedom to use, modify, and distribute it. Esbuild's blazing fast speed and support make this an attractive option for optimizing your project's bundling process.
All the vulnerabilities related to the version 0.17.9 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.