Esbuild, an incredibly fast JavaScript bundler and minifier, saw a minor version bump from 0.0.14 to 0.0.15 on April 7th, 2020. While both versions share the same MIT license and originate from the same GitHub repository, several key differences might influence a developer's decision to upgrade.
Firstly, the newer version, 0.0.15, exhibits an increase in both file count and unpacked size within its distribution package. Specifically, the file count jumps from 2 in version 0.0.14 to 3, and the unpacked size increases from 2199 bytes to 2463 bytes. Although the size increase is relatively small, this suggests the addition of at least one new file or modification to existing files, potentially introducing new features, bug fixes, or performance enhancements.
Secondly, version 0.0.15 was released roughly 1 hour and 30 minutes after version 0.0.14. The rapid succession of these releases hints at a critical fix or a quick follow-up to the initial release.
For developers, it's worth investigating the changelog or release notes (if available) to understand the exact nature of the changes included in version 0.0.15. Given Esbuild's focus on speed and efficiency, even minor updates can have a noticeable impact on build times and overall performance. Therefore, upgrading to the latest version is recommended to benefit from any potential improvements. While both are early versions (0.0.x), staying current ensures access to the most refined and optimized bundling experience.
All the vulnerabilities related to the version 0.0.15 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.