Esbuild versions 0.4.6 and 0.4.7 are closely related iterations of this extremely fast JavaScript bundler and minifier, both licensed under MIT. While the core feature set remains consistent, reflected in identical descriptions and the same number of files (6) and unpacked size (20349 bytes) in their respective tarballs, the crucial difference lies in their release dates. Version 0.4.7 was published on June 5th, 2020, at 04:12:13.464Z, approximately four hours after version 0.4.6, which was released on the same day at 00:50:14.839Z.
For developers leveraging esbuild to optimize their JavaScript build processes, this nuanced difference signals the possibility of bug fixes or minor improvements implemented between these releases. Considering the proximity of the release times, it's likely that 0.4.7 addresses issues discovered immediately after the 0.4.6 deployment. Developers should prioritize using the latest version (0.4.7 in this case) to benefit from any potential stability enhancements or refinements. This allows one to have a more robust build process when using the bundler. Esbuild simplifies and notably reduces the time it takes to bundle and minify JavaScript projects, making it a great tool for improving build times and overall development efficiency. Using the newer version of the two increases the probability of a more stable and optimized experience during the build process.
All the vulnerabilities related to the version 0.4.7 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.