Esbuild versions 0.11.2 and 0.11.3 represent iterative improvements to this exceptionally fast JavaScript bundler and minifier, designed for optimal web development workflows. Both versions share the same core characteristics: the MIT license, a git repository hosted on GitHub under evanw/esbuild, and a functionally similar distribution structure with a compact file count.
The key differentiating factor between the two lies in the release date and slight unpacked size difference. Version 0.11.3 was released on April 2nd, 2021, succeeding version 0.11.2 released on March 30th, 2021. The unpacked size of 0.11.3 is marginally larger at 81020 bytes compared to 81010 bytes for 0.11.2, indicating minor code adjustments, bug fixes, or performance enhancements.
For developers considering esbuild, the incremental nature of these updates suggests a focus on stability and continuous improvement. Upgrading from 0.11.2 to 0.11.3 likely introduces subtle refinements that enhance the overall bundling experience. Given esbuild's core promise of speed and efficiency, even small alterations can contribute to faster build times and optimized output, making it a valuable tool for enhancing productivity within modern JavaScript projects. Developers should consult the accompanying changelog for a comprehensive list of specific changes to fully utilize the improved tool if they are experiencing issues.
All the vulnerabilities related to the version 0.11.3 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.