Esbuild version 0.6.8 represents a minor update over its predecessor, version 0.6.7, in this extremely fast JavaScript bundler and minifier. Both versions maintain the same MIT license and are hosted on GitHub, ensuring continued community support and transparency. The core functionality of esbuild, focused on high-performance bundling and minification, remains consistent across both releases, making it appealing for developers seeking speed and efficiency in their build processes.
Notably, version 0.6.8 introduces a slight increase in unpacked size, reaching 26902 bytes compared to 25634 bytes in version 0.6.7. This subtle difference suggests potential enhancements or bug fixes that contribute to the improved overall package. Released on July 27, 2020, version 0.6.8 arrived very shortly after 0.6.7 which was released on July 25, 2020.
While the core value proposition of esbuild—speed and simplicity—is maintained, developers upgrading should be aware of the increment in package size and consider this when evaluating the impact on their project's dependencies. The relatively rapid release cycle suggests active development and a commitment to addressing issues or incorporating improvements swiftly. For developers prioritizing the latest refinements and potential bug fixes, updating to version 0.6.8 is recommended. However, given the minor nature of the release, projects already using esbuild 0.6.7 will experience minimal disruption when upgrading.
All the vulnerabilities related to the version 0.6.8 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.