Esno version 0.4.0 marks an evolution in running TypeScript and JavaScript Node.js applications with the speed and efficiency of esbuild. Comparing it to the previous stable version, 0.3.0, several key differences stand out, impacting developers seeking a smooth and performant development experience.
One significant change is the updated dependency on esbuild itself, moving from version 0.8.17 in 0.3.0 to ^0.8.29 in 0.4.0. This upgrade likely incorporates performance enhancements and bug fixes inherent in newer esbuild releases. Additionally, esbuild-register jumps from version 1.1.1 to ^1.2.1, suggesting improvements in how TypeScript and JavaScript files are registered and transformed during runtime.
Notably, version 0.3.0 relied on the esm package for module handling, which is completely removed in version 0.4.0. This indicates a shift in the internal architecture of esno, potentially streamlining the module resolution process and further optimizing performance. The removal of esm could simplify the dependency tree and reduce potential conflicts. While both versions maintain a small file count of four within their distributions, the unpacked size has slightly decreased in 0.4.0 suggesting possible refinements in the codebase. Developers should consider these updates for enhanced compatibility, improved speed, and a more modern approach to running TypeScript and JavaScript applications with esbuild. This package provides an excellent way to speed up your TS/JS Node development using esbuild.
All the vulnerabilities related to the version 0.4.0 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.