Esbuild version 0.12.4 builds upon the already impressive foundation laid by version 0.12.3, offering developers an even more refined and optimized experience with this incredibly fast JavaScript bundler and minifier. While both versions share the same core description and MIT license, subtle yet significant differences can be found in the details. Most notably the file size and release date.
The unpacked size indicates that version 0.12.4, with 89646 bytes, is slightly larger than version 0.12.3, which comes in at 88232 bytes. This suggests that the newer version incorporates either new features, enhanced optimizations, or modified bundled dependencies that contribute to this growth. The release date for version 0.12.4 is May 27, 2021, while version 0.12.3 was released on May 26, 2021. While only a difference of one day, it hints at potential bug fixes or quick improvements addressed in the later release.
Developers considering upgrading to esbuild 0.12.4 should examine the project's changelog or release notes for a comprehensive understanding of the specific changes made. The small difference in unpacked size could indicate performance improvements, bug fixes, or new features. Esbuild delivers outstanding build speeds and simplicity, these incremental updates further solidify its position as a top-tier choice for modern web development workflows. The combination of speed, ease of use, and continuous improvement makes esbuild a compelling choice for any project seeking to optimize build times.
All the vulnerabilities related to the version 0.12.4 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.