Esbuild, a lightning-fast JavaScript bundler and minifier, saw a new version released on August 17, 2020: version 0.6.25. Comparing it to the previous stable release, version 0.6.24 (released August 15, 2020), both versions share identical descriptions, licenses (MIT), repository links, file counts (6), and unpacked sizes (32114). This suggests the core functionality and fundamental assets of the esbuild package remained consistent between these two releases.
The primary difference lies in the release date. Version 0.6.25 was published approximately one day and nineteen hours after version 0.6.24. While the changelog isn't available within the provided data, the quick turnaround hints at a bug fix, a minor enhancement, or an update to dependencies. This makes 0.6.25 the more desirable version, especially for developers who encountered issues with 0.6.24.
For developers considering esbuild, it's crucial to check the official esbuild repository for detailed changelogs to understand the specific differences between these versions. This will allow a more informed choice, as it is important to always use the latest stable version to benefit from improved performance, bug fixes and security updates. Because of its speed and efficient bundling, esbuild is great for optimising web applications, and it stands out among other bundlers for its performance and ease of use.
All the vulnerabilities related to the version 0.6.25 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.