Esbuild 0.8.18 marks a minor version bump from 0.8.17 in the popular JavaScript bundler and minifier known for its exceptional speed. Both versions maintain the same core functionality: efficiently bundling and minifying JavaScript code under the MIT license, residing in the same GitHub repository, and exhibiting identical fileCount (6) and unpackedSize (57252) in their distributed tarballs. This suggests the changes introduced in 0.8.18 are likely concentrated within the bundled code itself, addressing bug fixes or minor performance enhancements rather than altering the package's structure or API.
The key difference lies in the release date. Version 0.8.18 was released on December 4th, 2020, roughly five days after version 0.8.17, which debuted on November 29th, 2020. This short interval between releases typically signifies a patch addressing immediate issues identified in the previous version.
For developers considering esbuild, this implies that while the core functionality remains stable between these two versions, opting for the newer 0.8.18 is generally advisable. It likely incorporates crucial fixes or optimizations discovered shortly after the release of 0.8.17, leading to a subtly improved and potentially more reliable build process. Always consult the official esbuild changelog on GitHub for the definitive list of changes between versions for an accurate list of what has changed.
All the vulnerabilities related to the version 0.8.18 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.