Esbuild version 0.8.42 introduces subtle yet potentially impactful changes compared to its predecessor, 0.8.41. Both versions uphold Esbuild's core promise: being an exceptionally fast JavaScript bundler and minifier, licensed under the MIT license for open-source flexibility. Developers relying on swift build times and efficient code optimization will find both versions valuable.
However, a key difference lies in the "unpackedSize," which increases slightly from 68,676 bytes in version 0.8.41 to 69,088 bytes in version 0.8.42. While seemingly minor, the 412-byte increment could signal internal adjustments, bug fixes, or minor feature enhancements. Developers should test the newer version in their specific projects to ensure compatibility and performance. The release date also offers a clue since it was release on February 5, 2021 while the previous was released on February 4, 2021. Such a close release schedule implies a rapid response to address immediate issues or introduce refinements. Both packages contain 6 files.
For developers, this means upgrading to 0.8.42 may provide incremental improvements or address edge cases encountered in 0.8.41. Always consult the changelog or commit history of the esbuild repository on GitHub to gain a deeper understanding of the specific changes implemented between these versions and assess their relevance to your project's needs.
All the vulnerabilities related to the version 0.8.42 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.