Esbuild version 0.8.0 represents a recent update to this extremely fast JavaScript bundler and minifier, succeeding version 0.7.22. Both versions maintain the same core purpose: efficiently bundling and minifying JavaScript code, licensed under the MIT license, and are accessible through the same GitHub repository. This makes upgrading relatively seamless for existing users.
The key difference between the two versions lies in the dist object, specifically the unpackedSize. Version 0.8.0 has an unpacked size of 40347 bytes, while version 0.7.22 is slightly larger at 40832 bytes. While seemingly minor, this potentially indicates optimizations or refinements in the bundling process in the newer version, potentially leading to a smaller final bundle size for developers. Both versions maintain the same file count in the distributed tarball.
Furthermore, the releaseDate field pinpoints that version 0.8.0 was released shortly after 0.7.22. This suggests that 0.8.0 contains bug fixes, minor improvements, or immediate responses to issues identified in the preceding version. Given the short time span between releases, developers should consider upgrading to 0.8.0 to benefit from the latest improvements and ensure they are building with the most up-to-date version of esbuild. This rapid iteration highlights the ongoing development and commitment to providing a high-performance bundler. For developers employing esbuild for its speed and efficiency, staying current with these updates is highly recommended.
All the vulnerabilities related to the version 0.8.0 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.