Esbuild version 0.8.33 represents a minor update to the popular JavaScript bundler and minifier, building upon the foundation laid by version 0.8.32. Both versions retain the same core characteristics: they are licensed under the MIT license, boast impressive speed for bundling and minifying JavaScript code, and are maintained within the same GitHub repository. The descriptions for both versions are identical, highlighting their shared purpose.
The key difference lies in the release date and unpacked size. Version 0.8.33 was released on January 18, 2021, a few days after version 0.8.32, which was released on January 14, 2021. While seemingly insignificant, the slight increase in unpacked size, from 63777 to 64262, suggests that version 0.8.33 likely incorporates minor bug fixes, performance improvements, or small feature additions compared to its predecessor. The fileCount remains consistent at 6 between the two versions.
For developers, this means that upgrading from 0.8.32 to 0.8.33 is likely a low-risk endeavor with potential benefits in terms of stability or performance. Given esbuild's focus on speed and efficiency, even small improvements can be worthwhile. Developers seeking the most up-to-date version of this fast bundler will want to use 0.8.33. While the specific changes are not detailed, the updated release date signals a refinement of the tool. Both versions are accessible via npm.
All the vulnerabilities related to the version 0.8.33 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.