Esbuild 0.15.6 represents a minor version update over 0.15.5 in this extremely fast JavaScript and CSS bundler and minifier. While both versions share the same core description and license information, the key difference lies in the dependency versions included within. Both versions include architecture-specific builds as dependencies and optional dependencies, such as esbuild-linux-64, esbuild-windows-64, esbuild-darwin-arm64, and many others, ensuring compatibility across various operating systems and architectures. The core esbuild package acts as a wrapper, delegating the actual bundling and minification tasks to the appropriate architecture-specific binary.
The update from 0.15.5 to 0.15.6 primarily involves bumping the versions of these architecture-specific dependencies from 0.15.5 to 0.15.6. This suggests that the update likely addresses bug fixes, performance improvements, or potentially new features within the underlying esbuild engine itself. Developers should upgrade to 0.15.6 to benefit from these refinements. Furthermore, the releaseDate indicates that 0.15.6 was released on August 30, 2022, roughly two weeks after 0.15.5 (August 17, 2022), highlighting the rapid development cycle and commitment to improvement. The unpackedSize also sees a small change, from 119556 bytes in version 0.15.5 to 119818 bytes in version 0.15.6, suggesting some changes, possibly new resources or code, have been added. Upgrading ensures developers leverage the latest optimizations and fixes in this popular build tool.
All the vulnerabilities related to the version 0.15.6 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.