Esbuild is a lightning-fast JavaScript bundler and minifier, designed for exceptional build performance. Version 0.6.10 follows closely on the heels of version 0.6.9, with very subtle changes distinguishing the two. Both versions maintain the core promise of speed and efficiency that developers have come to expect from esbuild, boasting a lightweight footprint with a compact unpacked size of around 29KB and delivered in a package containing just 6 files.
The crucial difference lies in the release timestamp. Version 0.6.10 was published on July 29, 2020, at 03:58:03.862Z, while version 0.6.9 was released just a couple of hours prior, on the same day at 01:48:35.728Z. This close proximity in release times suggests potential minor bug fixes or optimizations addressed in 0.6.10. While the exact nature of the change isn't explicitly detailed in the provided data, developers who prioritize stability and the most up-to-date fixes would likely benefit from opting for version 0.6.10. Regardless of the version, developers leveraging esbuild gain a powerful tool for streamlining their JavaScript build processes, resulting in faster development cycles and improved application performance. Both are MIT licensed.
All the vulnerabilities related to the version 0.6.10 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.