Esbuild versions 0.8.13 and 0.8.14 offer developers an exceptionally fast JavaScript bundler and minifier. Both versions, licensed under MIT, share the same core characteristics: rapid build times, efficient minification, and a streamlined approach to bundling web assets. They're available on npm and accessible through the familiar git repository. Digging deeper, both versions have similar sizes, containing 6 files and an unpacked size of 56336 bytes which show there wasn't a mayor change in these versions.
The key difference lies in the release dates. Version 0.8.13 was released on November 23, 2020, while version 0.8.14 followed shortly after on November 24, 2020. This suggests that version 0.8.14 is a minor patch or bug fix release addressing issues found in the preceding version.
For developers, choosing between these versions would likely depend on whether they encountered any problems with 0.8.13. If stability is paramount and 0.8.13 performed flawlessly, sticking with it might be reasonable. However, upgrading to 0.8.14 is generally recommended to benefit from any potential bug fixes or minor improvements introduced in that version, ensuring a smoother and more reliable bundling experience. Given the minimal time difference between releases, the upgrade is highly probable to be seamless.
All the vulnerabilities related to the version 0.8.14 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.