Esbuild versions 0.2.7 and 0.2.8 are closely related, both serving as "extremely fast JavaScript bundler and minifier" tools. Both versions, licensed under MIT, share the same origin repository on GitHub. Developers exploring esbuild can expect a consistent experience in terms of basic features and functionalities related to bundling and minifying JavaScript. The core description, license, repository, file count, and unpacked size remain unchanged between the two versions, suggesting a relatively stable project structure.
However, the key difference lies in the release dates. Version 0.2.8 was released on May 7, 2020, at 10:29:10.115Z, approximately two hours after version 0.2.7, which was released at 08:26:16.391Z on the same day. This indicates that version 0.2.8 is likely a patch release or a minor update addressing bugs or implementing small enhancements discovered shortly after the initial 0.2.7 release. While the immediate functionality might appear identical, developers should always favor the newer version (0.2.8) to benefit from any potential bug fixes or refinements introduced by the team, ensuring a smoother and potentially more reliable bundling and minification experience. Check the changelog for specific details on the bug fixes or improvements implemented between version 0.2.7 and version 0.2.8.
All the vulnerabilities related to the version 0.2.8 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.