Esbuild versions 0.4.8 and 0.4.9 are both iterations of the extremely fast JavaScript bundler and minifier, designed to significantly improve build times for web development projects. Both versions share similar characteristics, boasting a small unpacked size of just over 20KB and distributed as a compact tarball with a small file count. Both are MIT licensed, offering flexibility and freedom for developers to integrate esbuild into their projects. Also both versions share the same github repository.
The key difference between the two versions lies in their release dates: version 0.4.8 was released on June 5th, 2020, while version 0.4.9 followed shortly after, on June 7th, 2020. This close proximity suggests that version 0.4.9 likely contains bug fixes, performance improvements, or minor feature enhancements built upon the foundation of version 0.4.8.
For developers considering esbuild, either version offers considerable speed advantages compared to traditional bundlers. The rapid release of 0.4.9 following 0.4.8 implies a commitment to stability and continuous improvement. While the specific changes between these minor versions aren't detailed in the provided data, upgrading to the latest patch version (0.4.9) is generally recommended to benefit from the most recent fixes and optimizations. Developers should always consult the changelog or release notes on the project's GitHub repository for comprehensive details on the modifications implemented in each version. Ultimately, both 0.4.8 and 0.4.9 serve as robust options for developers seeking a high-performance JavaScript bundling solution.
All the vulnerabilities related to the version 0.4.9 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.