Esbuild version 0.6.11 represents a subtle yet potentially impactful update over its predecessor, version 0.6.10. While both versions brandish the same "extremely fast JavaScript bundler and minifier" description and MIT license, a closer look reveals key distinctions important for developers. Primarily, the unpacked size of version 0.6.11 is significantly larger, weighing in at 48302 bytes compared to 0.6.10's 29538 bytes, implying added functionality or refinement of existing features. This is further supported by the increased file count in the distribution tarball, from six files to seven.
For developers, this suggests that version 0.6.11 may offer enhanced capabilities, possibly including better support for specific JavaScript features, improved performance in certain bundling scenarios, or more robust error handling. It is advised that before upgrading, developers should review the changelog for 0.6.11 and consult any migration guides for potential breaking changes that could affect existing build processes. The nearly identical release dates – merely a day apart – indicate that 0.6.11 likely addresses immediate bug fixes or minor enhancements identified shortly after the 0.6.10 release. If you are using Esbuild, a jump to the newer version may give benefits.
All the vulnerabilities related to the version 0.6.11 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.