Esbuild is a blazing-fast JavaScript bundler and minifier designed to significantly improve build times for web development projects. Both versions 0.7.20 and 0.7.21 share the same core functionality, providing developers with an efficient tool to bundle and minify their JavaScript, TypeScript, and CSS files. The MIT license ensures broad usability across various projects, while the Git repository hosted on GitHub offers transparency and community contribution.
While the core description remains consistent, the key difference between versions 0.7.20 and 0.7.21 lies in their release dates. Version 0.7.21 was released on October 25, 2020, at 10:19:35.774Z, a few hours after version 0.7.20 which was released on the same day at 05:34:09.907Z. This suggests that version 0.7.21 likely contains bug fixes or minor improvements over its predecessor. Typically, such incremental updates address edge cases, performance tweaks, or security patches discovered in the earlier release.
For developers, upgrading to the latest patch version, in this case, 0.7.21, is generally recommended to benefit from the most stable and refined experience. Although the fileCount and unpackedSize remain identical between the two releases indicating no significant functional changes, adopting 0.7.21 ensures access to any immediate fixes implemented since the previous release, contributing to a more robust build process. Always review the changelog between any versions, accessing the project directly, to see the complete changes.
All the vulnerabilities related to the version 0.7.21 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.