Esbuild version 0.13.14 is a minor update to the extremely fast JavaScript and CSS bundler and minifier package. Compared to the previous stable version, 0.13.13, the core functionalities remain the same, focusing on speed and efficiency for web development build processes. Both versions support a wide range of target platforms, evident in their dependencies and optional dependencies, including various Linux distributions, macOS, SunOS, NetBSD, FreeBSD, OpenBSD, and Windows, catering to different architectures like 32-bit, 64-bit, ARM, and more.
The key difference lies in the updated dependency versions themselves. Specifically, while both list identical sets of dependencies (esbuild-linux-64, esbuild-darwin-arm64 and so on), version 0.13.14 utilizes the "0.13.14" version of these dependencies, while 0.13.13 uses the "0.13.13" versions. This means that while the core API and functionality likely remains unchanged, the underlying platform-specific binaries have been updated. This likely incorporates bug fixes, performance improvements, or security patches pertinent to those individual platform-specific packages. Developers should note the updated release date, indicating a refresh of the package with possibly recent fixes and tweaks. The unpacked size is slightly decreased which could imply that there are fewer files or some of the have been removed or packed better.
All the vulnerabilities related to the version 0.13.14 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.