Esbuild version 0.11.16 builds upon the solid foundation of its predecessor, version 0.11.15, both iterations centered around providing developers with an exceptionally fast JavaScript bundler and minifier. Both versions maintain the same MIT license and are accessible via the same GitHub repository, ensuring continuity and open-source accessibility for users.
A key difference lies in the release dates, with version 0.11.16 arriving on April 28, 2021, shortly after version 0.11.15 which was released on April 26, 2021. This suggests that version 0.11.16 likely incorporates bug fixes, minor enhancements, or urgent patches addressing issues discovered in the preceding version. While both versions share the same file count (6), a subtle difference exists in the unpacked size. Version 0.11.16 has an unpacked size of 86499 bytes, marginally larger than version 0.11.15's 86371 bytes. This small increase could indicate added functionalities, refined optimizations, or expanded feature sets within the newer version.
For developers, this means that upgrading to version 0.11.16 is likely a worthwhile endeavor. The focus for them is getting fixes and the newest features. Given the minimal time between releases, the upgrade should be seamless, while potentially addressing minor issues or bringing performance improvements. Esbuild's core promise of speed remains intact, as evidenced by the continued use of the same foundational architecture.
All the vulnerabilities related to the version 0.11.16 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.