Esbuild version 0.8.48 represents a minor update over its predecessor, version 0.8.47, within the fast-paced JavaScript bundler and minifier landscape. Both versions retain the same fundamental characteristics: the MIT license, the project's origin within the evanw/esbuild GitHub repository, a compact file count of 6 within the distributed tarball, and an identical unpacked size of 71318 bytes. This points toward focused refinements and bug fixes rather than substantial feature additions.
The key differentiator lies in the release date. Version 0.8.48 was published on February 18, 2021, at 14:17:11.398Z, approximately 12 hours and 13 minutes after version 0.8.47, which was released on the same day at 02:04:11.961Z. For developers relying on esbuild in their build processes, this signifies an effort to rapidly address identified issues or incorporate last-minute improvements. While the core performance benefits of esbuild – its extreme speed in bundling and minifying JavaScript – remain consistent between versions, upgrading to 0.8.48 is recommended to leverage any potential stability enhancements or minor bug resolutions implemented since 0.8.47. Therefore, users should consider this update to ensure they are using the most refined and up-to-date iteration of esbuild's capabilities, minimizing potential hiccups in their development workflow.
All the vulnerabilities related to the version 0.8.48 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.