Esbuild is a blazing-fast JavaScript bundler and minifier, designed to drastically improve build times for web development projects. Comparing versions 0.2.10 and 0.2.11, we observe a subtle but important update. Both versions share the same core characteristics: MIT license, identical unpacked size and file count in their distributions, meaning the structural makeup of the packages remains consistent.
The key distinction lies in their release dates. Version 0.2.11 was released on May 10, 2020, a day after version 0.2.10. Although the change log between them are not specified in the input, the quick succession between releases suggests that version 0.2.11 likely addresses bug fixes or minor improvements discovered shortly after the release of 0.2.10.
For developers, this means that upgrading from 0.2.10 to 0.2.11 is likely a worthwhile effort, especially when stability and reliability are paramount. While the exact nature of the changes may not be immediately apparent without consulting the full changelog, the updated version ensures developers benefit from the most up-to-date and potentially refined codebase. Esbuild's speed and efficiency continues to be a significant advantage promising faster builds whether you are using one or the other version. Always review the detailed changelog for comprehensive understanding of the updates.
All the vulnerabilities related to the version 0.2.11 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.