You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
Summary
esbuild allows any websites to send any request to the development server and read the response due to default CORS settings.
Details
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:
The attacker serves a malicious web page (http://malicious.example.com).
The user accesses the malicious web page.
The attacker sends a 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.The attacker gets the content of 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 byFetching /index.html: normally you have a script tag hereFetching /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
Connecting /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)))
Fetching URLs in the known file: once the attacker knows one file, the attacker can know the URLs imported from that file
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.
PoC
Download reproduction.zip
Extract it and move to that directory
Run npm i
Run npm run watch
Run fetch('http://127.0.0.1:8000/app.js').then(r =>r.text()).then(content => console.log(content)) in a different website's dev tools.imageImpactUsers using the serve feature may get the source code stolen by malicious websites.
The text was updated successfully, but these errors were encountered:
Description
如题, github总是提示esbuild有风险, 请升级至25.0.0以上

Reproduction
none
Used Package Manager
npm
System Info
The text was updated successfully, but these errors were encountered: