Esbuild versions 0.8.49 and 0.8.50 both function as extremely fast JavaScript bundlers and minifiers, licensed under the MIT license and maintained in the same GitHub repository. Both versions share identical descriptions and file metrics, including a file count of six and an unpacked size of 71,318 bytes.
The key difference lies in their release dates. Version 0.8.50 was released on February 21, 2021, while version 0.8.49 was released on February 19, 2021. Considering the proximity of these dates, the update from 0.8.49 to 0.8.50 likely includes bug fixes, performance enhancements, or possibly minor feature additions.
For developers utilizing esbuild, it's essential to stay updated with the latest minor releases for the benefits of stability and potential performance improvements. While the change log between these specific versions is not provided here, developers are encouraged to consult esbuild's official documentation and release notes for detailed information regarding the changes implemented in version 0.8.50. This allows for an informed decision on whether the incremental update is advantageous for their specific project needs. When integrating esbuild into the development workflow, remember its core function is to drastically speed up the bundling of JavaScript and related assets, resulting in faster build times and improved developer productivity.
All the vulnerabilities related to the version 0.8.50 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.