Esbuild version 0.8.22 represents a subtle yet noteworthy update to the lightning-fast JavaScript bundler and minifier, building upon the solid foundation of version 0.8.21. Both versions share the same core promise of extreme speed in bundling and minification, released under the permissive MIT license and maintained in the GitHub repository by evanw.
The most immediate difference for developers lies in the increased "unpackedSize," jumping from 58,550 bytes in version 0.8.21 to 62,543 bytes in version 0.8.22. While seemingly small, this nearly 4KB increment hints at internal improvements, bug fixes, or potentially new features introduced in the later version. This suggests developers might experience enhanced stability or access to refined functionality. Developers might also find updated dependencies on the updated version compared to the previous stable version of the tool.
Furthermore, the release date offers a temporal perspective. Version 0.8.22 arrived on December 12, 2020, succeeding version 0.8.21, released on December 8, 2020. The quick turnaround suggests that any changes included are likely incremental refinements rather than a seismic overhaul. For developers already leveraging esbuild, upgrading to 0.8.22 likely promises a slightly more polished and robust experience without introducing significant breaking changes. For new adopters, the speed and efficiency that esbuild provides makes it a great alternative to older and slower JavaScript bundlers.
All the vulnerabilities related to the version 0.8.22 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.