Esbuild versions 0.8.28 and 0.8.29 are both iterations of an exceptionally fast JavaScript bundler and minifier, designed to optimize web development workflows. While seemingly similar at first glance, as indicated by identical descriptions, license, repository details, file count and unpacked size (6), a key difference lies in their release dates. Version 0.8.29 was released on January 2, 2021, while version 0.8.28 was released on December 31, 2020.
For developers, this difference in release date, even if seemingly minor, suggestss that version 0.8.29 likely incorporates bug fixes, performance improvements, or potentially new features implemented after the release of version 0.8.28. Considering that both versions package identical content as evidenced by fileCount and unpackedSize it would make sense to expect improvements within the internal code.
Esbuild distinguishes itself with its speed in bundling and minifying Javascript code. Upgrading to the newer 0.8.29 version would be beneficial for developers looking for the most stable and performant version of the tool. It is difficult to know what the new version contains without looking at the release notes of the project, but it is common practice to expect improvements and bug fixes. Developers should prioritize using the newest stable version to gain advantage of constant optimization.
All the vulnerabilities related to the version 0.8.29 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.