Esbuild, the lightning-fast JavaScript bundler and minifier, saw a minor version bump from 0.7.17 to 0.7.18 on October 20, 2020. While both versions share the same MIT license and originate from the same GitHub repository, a few subtle differences exist. The unpacked size of version 0.7.18 is slightly larger at 39554 bytes compared to 0.7.17's 39339 bytes, suggesting possible additions or adjustments to the codebase. This difference, along with a later release date, means developers might find bug fixes or incremental improvements in the newer version.
For developers choosing between the two, version 0.7.18 represents the slightly more up-to-date option. While the core functionalities of bundling and minifying JavaScript with exceptional speed remain consistent, the small incremental size difference likely addresses edge cases or refines existing features. If encountering issues with 0.7.17 or seeking the most current iteration of the tool, opting for 0.7.18 makes practical sense for a developer, and could provide updated features beyond the increased size. Both versions offer a compelling alternative to slower JavaScript build tools, and allow for quicker development.
All the vulnerabilities related to the version 0.7.18 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.