Esbuild version 0.6.12 follows swiftly on the heels of version 0.6.11, both iterations of this extremely fast JavaScript bundler and minifier under the MIT license. While the core functionalities remain consistent – offering developers a high-performance solution for bundling and minifying JavaScript code – the key difference lies in the release timing. Version 0.6.12 was published on July 31, 2020, just a day after version 0.6.11's release on July 30, 2020. This short interval suggests that version 0.6.12 likely addresses minor bugs, incorporates small improvements, or resolves any immediate issues discovered in 0.6.11. For developers, this iterative approach signifies a commitment to stability and rapid issue resolution.
Both versions share the same file count (7) and unpacked size (48302 bytes), indicating no significant structural changes to the package itself. Both versions are available through the npm registry via their respective tarballs. Developers relying on esbuild should, as a general practice, consult the official esbuild GitHub repository and its associated changelog for detailed patch notes and a comprehensive understanding of the specific modifications introduced in version 0.6.12. Even iterative updates contribute to a more polished and reliable developer experience.
All the vulnerabilities related to the version 0.6.12 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.