Esbuild versions 0.5.21 and 0.5.22 showcase the incremental improvements typical of software development. Both versions maintain the core functionality of esbuild as a blazing-fast JavaScript bundler and minifier, licensed under the MIT license and hosted on GitHub. Developers already familiar with esbuild will find the upgrade from 0.5.21 to 0.5.22 relatively seamless.
The key difference lies in the details. Version 0.5.22, released on July 6th, 2020, compared to version 0.5.21 released on July 5th, 2020, represents a refinement of the existing codebase. While both versions comprise 6 files in the distributed tarball, version 0.5.22 exhibits a slightly larger unpacked size of 21882 bytes, an increase from the older version's 20721 bytes which it indicates an addition of features or bug fixes.
This difference, while seemingly small, likely reflects bug fixes, performance enhancements, or minor feature additions implemented in the newer version. For developers, updating to 0.5.22 is generally recommended to leverage the improved stability and potential performance gains. While a detailed changelog would provide more specific insights, the increased size suggests that the update is not merely a cosmetic change. Developers employing esbuild in production environments should test the new version thoroughly to ensure compatibility and optimal performance within their specific workflows.
All the vulnerabilities related to the version 0.5.22 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.