Esno version 0.15.0 represents a significant shift in the way the package handles TypeScript and JavaScript execution, powered by esbuild. Most notably, it introduces tsx as a core dependency, replacing the previous suite of esbuild related packages like esbuild, cross-spawn, esbuild-register, and esbuild-node-loader. This transition suggests a move towards a simplified and potentially more efficient implementation.
Developers familiar with older versions (like 0.14.1) which rely on the esbuild-* ecosystem, will find that version 0.15.0 streamlines the process. The removal of multiple esbuild related dependencies and adoption of tsx as a single dependency, promises a lighter dependency footprint and could potentially improve build times. While both versions share the same development dependencies like zx, fsxx, and typescript, emphasizing their commitment to testing and TypeScript support, the core runtime environment appears fundamentally different in 0.15.0 with streamlined dependency usage. This newer version prioritizes a more direct and concise approach via tsx for handling TypeScript and JavaScript execution within a Node.js environment. Developers currently reliant on specific configurations or behaviors of the esbuild-* packages might need to adjust their workflows when upgrading. The unpacked size of version 0.15.0 is also considerably smaller (2509) than 0.14.1 (3396) suggesting a more streamlined dependency model using tsx.
All the vulnerabilities related to the version 0.15.0 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.