Esbuild version 0.10.1 is a minor release update to the incredibly fast JavaScript bundler and minifier, building upon the solid foundation of version 0.10.0. Both versions share the same core strengths: blazing speed, thanks to its go-based implementation, and a developer-friendly experience. They offer capabilities such as ES module and CommonJS format support, tree shaking, code minification, and source map generation. The licensing remains MIT, ensuring you can confidently utilize esbuild in a wide array of projects, both personal and commercial.
The key difference lies in the details. Version 0.10.1, released just a day after 0.10.0, brings with it refinements and likely bug fixes, contributing to overall stability and potentially addressing specific edge cases encountered by users. While the core functionality remains consistent, upgrading to 0.10.1 is generally recommended to benefit from these improvements. The unpacked size of the newer version is slightly larger (80720 bytes versus 77082 bytes), hinting at additional features enhancements or code optimization implemented. Developers should consider this update as a routine maintenance, ensuring they leverage the most current and reliable build of esbuild optimizing performances for their projects when bundling and minifying their code. The difference of one day in the release dates highlighten the effort put in the package by the developers.
All the vulnerabilities related to the version 0.10.1 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.