Esbuild version 0.5.25 represents a minor update to the blazing-fast JavaScript bundler and minifier, following closely on the heels of version 0.5.24. Both versions maintain the core promise of exceptional speed for bundling and minifying JavaScript code, a key differentiator for developers seeking to optimize their build processes. They share the same MIT license, ensuring open-source flexibility, and connect to the same GitHub repository.
Although the descriptions are identical, a closer examination reveals subtle differences. The unpacked size of version 0.5.25 is slightly larger, weighing in at 22174 bytes compared to 0.5.24's 21950 bytes. This suggests that internal tweaks or additions to the codebase have been implemented in the newer version. Furthermore, version 0.5.25 was released more recently, with a release date of July 8th, 2020, whereas version 0.5.24 came out on July 7th, 2020.
For developers, the primary advantage of using esbuild lies in its unparalleled speed. This makes it an attractive tool for large projects where build times can significantly impact development velocity. While the differences between versions 0.5.24 and 0.5.25 are marginal according to the present data, opting for the newer version generally benefits from potential bug fixes and minor performance enhancements from the continuous effort of the package. Developers should consult the project's changelog on GitHub for a comprehensive overview of the specific changes introduced in version 0.5.25, enabling them to take full advantage of the latest improvements.
All the vulnerabilities related to the version 0.5.25 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.