Esbuild version 0.2.2 arrives swiftly after version 0.2.1, showcasing rapid development and a commitment to improvement in this extremely fast JavaScript bundler and minifier. Both versions maintain the MIT license, reassuring developers of its open and permissive usage rights, and are accessible via the same established GitHub repository, hinting at a stable and well-managed project.
A primary subtle distinction lies in the unpackedSize. Version 0.2.2 registers a minor increase in size (17627 bytes) compared to version 0.2.1 (17481 bytes). This suggests the introduction of new features, optimizations, or bug fixes that required a slightly larger footprint. Developers should be aware of this if size is a critical constraint in their deployment environment, though the difference remains marginal. Furthermore, the updated release date, showing a release only hours after the previous version, highlights the agility of the development team in addressing issues or deploying enhancements.
While the core description remains consistent between the two versions, the quick succession of releases indicates a project that's actively being refined. Developers using esbuild should consider reviewing the changelog, typically available in the project's GitHub repository, to understand the specific changes implemented in version 0.2.2 and assess their impact on their projects. Upgrading will grant access to these most recent enhancements and potential bug fixes. Given the small version difference, developers may expect a low risk of breaking changes during the update while benefiting from the freshest improvements in this increasingly popular build tool.
All the vulnerabilities related to the version 0.2.2 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.