Esbuild version 0.8.7 is a minor update to the blazing-fast JavaScript bundler and minifier, building upon the foundation laid by version 0.8.6. Both versions boast identical descriptions and licensing under the MIT license, reinforcing their commitment to providing a performant and freely usable tool for developers. They share the same repository URL on GitHub, signifying a continuation of development within the existing project structure.
The key distinctions lie in the "dist" section and the "releaseDate". Version 0.8.7 was released on November 13, 2020, while version 0.8.6 was released a couple of days before, on November 11, 2020, indicating a quick iteration cycle. The tarball URL reflects the version-specific archive location on the npm registry. Both versions consist of six files. However, the unpacked size has slightly decreased from 51196 bytes in version 0.8.6 to 50289 bytes in version 0.8.7. This suggests potential optimizations in the codebase, potentially leading to smaller bundle sizes or more efficient memory usage.
For developers, this minor update might include bug fixes, performance tweaks, or minor feature improvements introduced in the 0.8.7 version. Upgrading from 0.8.6 to 0.8.7 appears to be a low-risk operation. Developers should consult the changelog between the 2 versions for a detailed breakdown of changes. The promise of esbuild remains consistent: speed and efficiency in bundling and minifying JavaScript code, making it a compelling choice for web development projects where performance is paramount.
All the vulnerabilities related to the version 0.8.7 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.