Esbuild version 0.11.22 represents a subtle but noteworthy iteration in the evolution of this blazing-fast JavaScript bundler and minifier. While both versions 0.11.21 and 0.11.22 share the same core characteristics – MIT license, identical unpacked size and file count in the distribution package, and a consistent description highlighting its extreme speed – the key differentiator lies in the release date. Version 0.11.22 was published on May 15, 2021, a single day after version 0.11.21.
This suggests that 0.11.22 likely contains bug fixes, performance enhancements, or minor adjustments introduced specifically for stability and reliability based on user feedback or internal testing following the 0.11.21 release. For developers relying on esbuild for critical bundling and minification tasks, even seemingly small version increments can be significant. In this instance, upgrading to 0.11.22 is recommended to benefit from the latest refinements and ensure a smoother build process. The esbuild remains a top choice for optimizing website performance and reducing load times by efficiently packaging and minimizing JavaScript code, leading to an improved user experience. Choosing between the two versions means prioritizing a single day of potential refinements and fixes in a fast evolving environment.
All the vulnerabilities related to the version 0.11.22 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.