Esbuild, a blazing-fast JavaScript and CSS bundler, released version 0.15.16 following closely on the heels of version 0.15.15. While the core functionality remains consistent, subtle differences exist that developers should note. Both versions share the same core dependencies and optional dependencies. These dependencies are a range of platform-specific builds, like esbuild-linux-64, esbuild-windows-32, and @esbuild/linux-loong64, ensuring esbuild works across diverse operating systems and architectures. Both versions support an extensive assortment of platforms, attesting to esbuild's broad compatibility. These include Linux (various architectures), macOS (both Intel and Apple Silicon), Windows, and other more obscure systems, such as FreeBSD, NetBSD, and OpenBSD.
The key difference lies in the release date: version 0.15.16 was released on November 27, 2022, while version 0.15.15 was released on November 21, 2022. This suggests that version 0.15.16 likely incorporates bug fixes or minor improvements discovered since the previous release. The unpacked size is also slightly different with 0.15.16 being 121210 and 0.15.15 being 120851. Therefore the newest version is likely to contain improvements making it more stable. For developers already using esbuild, upgrading to 0.15.16 is advisable to benefit from these potential enhancements. When starting new projects, opting for the latest version ensures a more robust and refined build process from the outset. Both versions, licensed under MIT and hosted on GitHub, underscore esbuild's commitment to open-source principles and community collaboration.
All the vulnerabilities related to the version 0.15.16 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.