Esbuild version 0.8.34 marks a minor update from its predecessor, version 0.8.33, in the fast-paced world of JavaScript tooling. Both versions maintain their core identity as an extremely fast JavaScript bundler and minifier, licensed under the permissive MIT license, making them attractive choices for developers conscious of build times and open-source compatibility. The repository remains constant, hosted on GitHub under the evanw/esbuild project.
Examining the dist parameters reveals subtle similarities. The fileCount is identical at 6, and the unpackedSize is also the same at 64262 bytes, pointing to no significant changes in the core file structure or overall library size. This suggests that the update doesn't introduce sweeping new features or substantial alterations to the architectural footprint.
The most apparent, and arguably most crucial, difference lies in the releaseDate. Version 0.8.34 was published on January 21, 2021, whereas version 0.8.33 was released on January 18, 2021. This 3-day gap signifies that version 0.8.34 likely incorporates bug fixes, minor performance improvements, or very targeted enhancements implemented after the 0.8.33 release. For developers seeking the most stable and up-to-date experience, even within a rapidly evolving ecosystem, opting for version 0.8.34 offers a marginal benefit; it represents the bleeding edge of refinements built upon the already solid foundation of esbuild's bundling capabilities. While the impact on code processing is negligible, choosing the latest version ensures access to recent bug fixes and fine-tuned optimizations.
All the vulnerabilities related to the version 0.8.34 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.