Esbuild 0.11.5 represents a minor version update to the blazing-fast JavaScript bundler and minifier, succeeding version 0.11.4. While both versions share the same core mission of providing incredibly swift build times, promising significant improvements in developer workflow, version 0.11.5 incorporates subtle enhancements and refinements. The package size shows a slight increase in unpacked size from 81029 to 81483, so potentially developers would see minor improvements or bugfixes.
Specifically, developers upgrading from 0.11.4 to 0.11.5 can anticipate improvements related to bug fixes and fine-tuned performance tweaks. The release occurring on April 3, 2021, with only approximately 21 hours between the two versions, suggests that 0.11.5 fixes some immediate issues identified in 0.11.4.
For developers seeking optimal build performance and a streamlined bundling experience, Esbuild continues to be a compelling choice. Given the rapid succession of these two versions, it is recommended to choose the later version 0.11.5 and get the latest bug fixes and performance improvements. The library, licensed under MIT, remains an accessible and powerful tool for modern JavaScript development, delivering on its promise of speed and efficiency. As always, carefully review the detailed changelog and commit history for any potentially breaking changes to ensure a seamless upgrade.
All the vulnerabilities related to the version 0.11.5 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.