Esbuild versions 0.5.6 and 0.5.5 represent incremental updates in this exceptionally fast JavaScript bundler and minifier. Both versions share the same core attributes: MIT licensing, identical repository origins on GitHub, and comparable distribution sizes, each containing six files and unpacking to 19309 bytes. The key difference lies in their release dates. Version 0.5.6 was published on June 20, 2020, at 17:46:44 UTC, approximately nine hours after version 0.5.5, which was released at 08:47:46 UTC on the same day.
For developers, while these updates may seem subtle, they could encompass important bug fixes, performance improvements, or minor feature enhancements. Such incremental releases often address edge cases or compatibility issues discovered in the preceding version. When choosing between these versions, reviewing the changelog or release notes on the esbuild GitHub repository is crucial. Developers valuing stability and the latest refinements should opt for version 0.5.6. However, if already employing 0.5.5 without encountering issues, the immediate need to upgrade may be less pressing. Always prioritize testing any update within your specific project context to ensure seamless integration and prevent unexpected regressions. Because esbuild is prized for its speed and simplicity, these iterative releases likely contribute towards an even more refined developer experience.
All the vulnerabilities related to the version 0.5.6 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.