Esbuild, a blazing-fast JavaScript and CSS bundler, released version 0.18.1 shortly after version 0.18.0, showcasing its commitment to rapid iteration and improvement. While both versions share the same core description and functionality, the key difference lies primarily in the updated dependency versions for various platform-specific builds. Both the dependencies and optionalDependencies sections reflect this change, all platform-specific packages like @esbuild/linux-x64, @esbuild/darwin-arm64, and similar, have been bumped from version 0.18.0 to 0.18.1.
For developers, this means a potential refinement in platform-specific performance and bug fixes, although the nature of these changes isn't explicitly detailed in the provided metadata. Consider upgrading if you're experiencing platform-specific issues or simply want to benefit from the latest enhancements. The fileCount and unpackedSize remain consistent, suggesting code size and overall complexity were not significantly altered. Both versions are licensed under the MIT license and the github repository remains the same. The release date confirms the speed of the iterations of the versions, with less than 3 days between them. Always check the official esbuild release notes for a detailed breakdown of the changes contained within the 0.18.1 release.
All the vulnerabilities related to the version 0.18.1 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.