Esbuild, a blazing-fast JavaScript and CSS bundler and minifier, has a new version out: 0.17.8. Comparing it to the previous stable release, 0.17.7, reveals subtle but essential changes for developers seeking peak performance. Both versions maintain the same core description, licensing (MIT), and repository details, emphasizing the project's stability and open-source commitment. They also share an identical unpacked size of 129954 and file count of 7 in their distributed tarballs, suggesting no significant structural changes in the codebase itself.
The primary difference lies in the version numbers of the dependencies and optional dependencies. Both dependencies and optionalDependencies in version 0.17.8 point to @esbuild/* packages at version 0.17.8, a direct upgrade from 0.17.7 in the older release. This signifies targeted updates and bug fixes within Esbuild's platform-specific binaries, critical for optimal performance across diverse operating systems and architectures. These include Linux (arm, x64, arm64, ia32, ppc64, s390x, loong64, riscv64, mips64el), Windows (x64, ia32, arm64), macOS (x64, arm64), Android (arm, x64, arm64), FreeBSD (x64, arm64), NetBSD (x64), SunOS (x64), and OpenBSD (x64).
Crucially, the release date for 0.17.8 is February 13, 2023, a few days after the February 9, 2023 release of 0.17.7. This short interval implies that the newer version likely addresses immediate concerns or refinements identified shortly after the previous release. Developers should upgrade to 0.17.8 to benefit from these improvements, ensuring the most stable and performant bundling experience.
All the vulnerabilities related to the version 0.17.8 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.