Esbuild version 0.12.8 represents a subtle but potentially impactful update over version 0.12.7 of this remarkably fast JavaScript bundler and minifier. Both versions retain the MIT license, ensuring developer-friendly usage. They share the same core description, highlighting esbuild's primary goal of speed and efficiency in bundling and minifying JavaScript code for web development. The repository remains consistent, indicating stability in project governance.
The most apparent differences lie in the "dist" section and the release date. Version 0.12.8 was released on June 9, 2021, a single day after version 0.12.7. Both versions contain the same amount of files, but the "unpackedSize" differs slightly, with 0.12.8 being marginally larger (88440 bytes compared to 88233 bytes). This difference, though small, suggests that bug fixes, peformance improvements, or minor features were introduced. For developers, this change could mean improved stability or slight performance gains in their build process. Since the semver major and minor versions are the same, chances of breaking changes are low, so we can assume it's a patch upgrading dependencies or fixing bugs under the hood.
Developers should consider upgrading to version 0.12.8 to benefit from these improvements, ensuring they are using the most up-to-date version of this crucial build tool. Always review the changelog when upgrading minor versions within esbuild to catch any possible breaking changes.
All the vulnerabilities related to the version 0.12.8 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.