Esbuild 0.18.13 is a minor version bump from 0.18.12 in this extremely fast JavaScript and CSS bundler and minifier. The core description of the library remains unchanged: it's focused on speed and efficiency in bundling web assets. Looking at the json data, the most notable difference lies in the version numbers of the dependencies and optional dependencies. Both versions list an extensive set of platform-specific packages (e.g., @esbuild/linux-x64, @esbuild/win32-arm64) as both dependencies and optional dependencies.
For developers, this means the update likely includes bug fixes and/or performance improvements within these platform-specific builds. While no new features are explicitly mentioned in the metadata, upgrading from 0.18.12 ensures you're leveraging the latest optimizations across various operating systems and architectures. The unpackedSize of the dist folder grew just a little, from 130,687 to 131,049, indicating perhaps some small code changes, perhaps in the dependency packages. The releaseDate also shows that 0.18.13 was released just two days after 0.18.12, further pointing to a quick fix or minor enhancement update. A developer using esbuild should upgrade to 0.18.13 to get the benefits of any bug fixes and/or performance improvements. This upgrade should come with minimal risk, as there are no listed breaking changes. Always consult the offical changelog for detailed release notes.
All the vulnerabilities related to the version 0.18.13 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.