Esbuild 0.17.12 is a minor version update to the extremely fast JavaScript and CSS bundler, building upon version 0.17.11. Both versions share the same core functionality and description, focusing on speed and efficiency in bundling and minifying web assets. The primary difference lies in the version numbers of their dependencies. Both versions list identical sets of dependencies and optional dependencies, encompassing a wide range of platform-specific builds under the @esbuild namespace, such as @esbuild/linux-x64, @esbuild/win32-arm64, and @esbuild/darwin-arm64, catering to diverse operating systems and architectures, including Linux, Windows, macOS, Android, and FreeBSD. Each dependency or optional dependency, however, gets an updated version number equal to the esbuild version.
For developers, this update likely includes bug fixes, performance improvements, and possibly minor feature enhancements within the esbuild core and its platform-specific builds. While the core description remains the same, indicating no major API changes, developers should consult the official esbuild changelog or release notes for a detailed breakdown of specific fixes and enhancements included in 0.17.12. Given esbuild's reputation for rapid iteration and performance focus, even minor version updates are often worthwhile for developers seeking the fastest and most efficient build processes for their JavaScript and CSS projects. Checking the changelog for specifics will help ensure a smooth transition and maximize the benefits of the update.
All the vulnerabilities related to the version 0.17.12 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.