Esbuild is a blazing-fast JavaScript bundler and minifier, designed to significantly improve build times for web development projects. Version 0.12.25, released on September 2, 2021, follows closely on the heels of version 0.12.24, which was released on August 27, 2021. While both versions share the same MIT license and core functionality, there are subtle differences developers should be aware of.
Notably, version 0.12.25 exhibits a slight increase in unpacked size (89183 bytes) compared to version 0.12.24 (89145 bytes). This suggests internal changes or optimizations that, while minor, might contribute to enhanced performance or bug fixes. The file count remains consistent at 6 for both versions, indicating that the overall structure of the package hasn't been drastically altered.
For developers considering upgrading, the short release cycle implies potentially important bug fixes or incremental improvements in 0.12.25. Examining the changelog or commit history between these specific versions on the esbuild GitHub repository (https://github.com/evanw/esbuild) is recommended to pinpoint the exact nature of the changes. Esbuild's speed makes it an attractive option for projects of all sizes, and staying up-to-date with the latest releases ensures access to the best possible performance and stability. Always remember to test your builds after upgrading any dependency, including a bundler as critical as esbuild.
All the vulnerabilities related to the version 0.12.25 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.