Esbuild version 0.11.0 represents a step forward from version 0.10.2 in the evolution of this exceptionally fast JavaScript bundler and minifier. While both versions share the same core functionality – enabling developers to quickly bundle and minify their JavaScript code – there are subtle but potentially impactful differences.
The most immediate distinction lies in the release dates. Version 0.11.0 was published on March 29, 2021, slightly after version 0.10.2 released on March 27, 2021, marking a rapid iterative cycle for the project. Although the core description and licensing remain consistent between the two versions, under the MIT license, the newer version suggests bug fixes, performance tweaks, or minor feature additions.
Subtle differences in the "dist" object like "unpackedSize" of 81010 bytes in the newer version as opposed to the 80720 bytes of the older version might reflect the inclusion of new assets or code refinements. For developers, these small modifications can translate to improved stability or optimized build processes. Depending on the size and complexity of the target audience project, developers should also take note of the changes in the latest release to make informed decisions when upgrading versions. Esbuild continues to provide a compelling solution for optimizing JavaScript workflows.
All the vulnerabilities related to the version 0.11.0 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.