Esbuild version 0.2.5 is a minor update to the popular JavaScript bundler and minifier, following closely on the heels of version 0.2.4. Both versions aim to provide extremely fast build times for web development projects, a key advantage for developers seeking to optimize their workflow. The core functionality remains consistent: efficiently bundling JavaScript, TypeScript, and other web assets, as well as minifying code for production deployments. Both releases are licensed under the MIT license, encouraging widespread adoption and modification.
The key difference between the two versions lies in the increase in unpackedSize, incrementing from 17632 bytes (v0.2.4) to 18443 bytes (v0.2.5). While seemingly small, this 811 byte difference could signify minor bug fixes, performance tweaks, or small feature enhancements implemented in the 0.2.5 release. Developers considering upgrading should weigh the potential benefits of these refinements against any possible compatibility concerns, though such concerns are rare for minor version jumps.
Both versions are open-source, with their source code and contribution guidelines hosted on GitHub. The releaseDate also hints at the rapid iteration and active development behind esbuild. Because of the increase of the unpackedSize, developers are encouraged to upgrade to esbuild@0.2.5.
All the vulnerabilities related to the version 0.2.5 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.