Esbuild version 0.9.2 follows closely on the heels of version 0.9.1, both iterations of this remarkably fast JavaScript bundler and minifier. At a glance, the core attributes like description, license (MIT), and repository remain consistent, signaling no fundamental shift in the project's direction or licensing. The "dist" section, particularly the "fileCount" and "unpackedSize," are identical across both versions, at 6 files and 70208 bytes respectively. This suggests that the core codebase didn't undergo significant structural changes between these releases.
The primary difference lies in the release date. Version 0.9.1 was released on March 12, 2021, at 10:14:50 UTC, whereas version 0.9.2 followed later the same day at 20:25:56 UTC. This relatively rapid succession suggests that version 0.9.2 likely addresses bugs or minor issues discovered shortly after the 0.9.1 release. For developers, this means that while both versions share the same core functionality and excellent performance, choosing 0.9.2 is generally advisable. It almost certainly incorporates fixes, offering a potentially more stable experience right out of the gate. Given the speed of the update, it's unlikely to contain monumental changes, which minimizes the risk of introducing unforeseen issues in existing workflows. Essentially, 0.9.2 is a refined and likely more robust version of the already potent esbuild 0.9.1.
All the vulnerabilities related to the version 0.9.2 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.