Esbuild, a blazingly fast JavaScript bundler and minifier, saw a recent update from version 0.8.16 to 0.8.17 on November 29, 2020. While seemingly a minor version bump, even small changes can impact developers relying on its speed and efficiency for their build processes.
Looking at the metadata, the unpacked size difference between versions is minimal (57252 vs 57210 bytes), suggesting the update likely involves bug fixes or small feature enhancements rather than a major overhaul. Considering the short time frame between releases (November 26th to 29th), performance improvements wouldn't be out of the question either. Developers should investigate the changelog on the esbuild GitHub repository to pinpoint the exact modifications.
For developers already leveraging esbuild, upgrading to 0.8.17 is recommended to benefit from any bug fixes and potential performance gains. If integrating esbuild into a new project, starting with the latest version ensures you're building on the most stable and up-to-date foundation. Esbuild's MIT license provides broad usage rights, making it suitable for both personal and commercial projects. Remember to always check the official documentation and release notes for detailed information on each version.
All the vulnerabilities related to the version 0.8.17 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.