Esbuild version 0.17.13 represents a subtle update to the popular JavaScript and CSS bundler, following closely on the heels of version 0.17.12. A key difference lies in the release date, with 0.17.13 being published on March 24, 2023, a week after 0.17.12 released on March 17, 2023. From a developer's perspective, the core functionality remains consistent. Both versions are designed for exceptionally fast bundling and minification, a hallmark of the esbuild library. The package dependencies and optional dependencies are where the versions are actually different, each dependency was updated to the version of the package. Esbuild continues to support a wide range of platforms with dedicated pre-built binaries, evident from the extensive list of @esbuild/* packages tailored for various operating systems and architectures, including Linux, Windows, macOS, Android, and FreeBSD. Esbuild strives to achieve cross-platform compatibility. The MIT license ensures flexibility for developers, and the project's repository remains accessible via its GitHub. The dist object reveals that the archive structure and unpacked size remain the same between versions, hinting that the core build process and file organization are unchanged other than the bump to the dependency versions. For developers, this likely means a bug fix or small improvement is introduced justifying the new minor version. When upgrading ensure to consider the changes to the dependencies used.
All the vulnerabilities related to the version 0.17.13 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.