Esbuild is a blazing-fast JavaScript bundler and minifier, and versions 0.8.31 and 0.8.32 showcase its continued evolution. Both versions share the same core functionality, offering developers an MIT-licensed tool for efficient code bundling and minification, crucial for optimizing web application performance. They are hosted on GitHub under the evanw/esbuild repository, ensuring open collaboration and community contributions. The main difference between these two version is the "unpackedSize" on the dist object. Version 0.8.32 is slightly larger, with an unpacked size of 63777, compared to the 61851 of version 0.8.31. This increase in size might indicate new features, performance enhancements, or bug fixes included in the newer release. Although the file count remains consistent at 6 for both versions, the added size suggests internal modifications. Developers should prefer to use always the latest version for stability and best performance. The release dates highlight the rapid development cycle of esbuild, with version 0.8.32 being released approximately one week after 0.8.31. This frequent release cadence signals ongoing improvements and a commitment to providing developers with a cutting-edge bundling solution. For JavaScript developers aiming to optimize build times and improve website loading speeds, esbuild, especially version 0.8.32, represents a compelling option, offering speed and efficiency in a compact package.
All the vulnerabilities related to the version 0.8.32 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.