Esbuild version 0.3.0 represents a notable update from version 0.2.12 of this JavaScript bundler and minifier, boasting improvements relevant to developers seeking efficiency and speed in their build processes. Both versions share the same core description: an "extremely fast" tool for bundling and minifying JavaScript. They are also both released under the MIT license and maintained within the same GitHub repository.
A subtle but potentially impactful difference lies in the unpackedSize of the packages. Version 0.3.0 has an unpacked size of 18773 bytes, a tiny reduction from version 0.2.12's 18774 bytes. While seemingly insignificant, this slight decrease could reflect minor optimizations within the codebase. More significantly, comparing releaseDate shows us that the current version was released about 2 hours later than the previous version.
For developers choosing between these specific versions, it's crucial to consult the official esbuild changelog or release notes to gain a comprehensive understanding of the specific changes, bug fixes, and new features introduced in version 0.3.0. Minor updates like this often contain under-the-hood improvements that contribute to a more stable and performant experience, making the newer version generally preferable. Always prioritize reviewing the official documentation to assess the impact on your specific project and dependencies.
All the vulnerabilities related to the version 0.3.0 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.