Esbuild is an extremely fast JavaScript and CSS bundler and minifier, and comparing versions 0.14.18 and 0.14.19 reveals a subtle but important update. Both versions share the same core functionality for bundling and minifying code, aiming for optimal performance. They also boast identical dependency structures, with platform-specific binaries like esbuild-linux-64 and esbuild-darwin-arm64 to ensure compatibility across diverse operating systems and architectures. These dependencies are both required and optional, reflecting esbuild's robust approach to accommodating various environments, like Linux (32/64 bit, ARM, ARM64, s390x, ppc64le, mips64le), SunOS, Darwin (64 bit, ARM64), NetBSD, FreeBSD (64 bit, ARM64), OpenBSD, Android (ARM64) and Windows (32/64 bit, ARM64).
The key difference lies in their release dates, with version 0.14.19 arriving on February 6, 2022, after version 0.14.18 released on February 2, 2022. The identical dependencies and descriptions between the two versions suggest that 0.14.19 likely contains bug fixes, performance improvements, or minor adjustments that don't necessitate changes to the core dependency structure. For developers, upgrading to 0.14.19 is recommended to benefit from these potential refinements, ensuring a smoother and potentially more efficient bundling experience. The fileCount and unpackedSize remain the same, indicating that the core file structure and size haven't significantly changed. Therefore, the update is likely focused on internal improvements. Both versions are released under the MIT license.
All the vulnerabilities related to the version 0.14.19 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.