Esbuild version 0.8.57 is a minor update to the blazing-fast JavaScript bundler and minifier, following closely on the heels of version 0.8.56. Both versions maintain the core promise of esbuild: extremely fast build times and efficient code optimization for modern web development. The license remains under the permissive MIT license. Developers already familiar with esbuild will find the upgrade seamless, as the fundamental usage and core features are consistent between these releases.
While the descriptions and repository details remain identical, a key difference lies in the release date. Version 0.8.57 was released on March 8th, 2021, just a few days after version 0.8.56, which came out on March 5th, 2021, suggesting a quick follow-up release perhaps addressing minor bug fixes or performance tweaks. Another subtle, but potentially impactful difference is the unpacked size. Version 0.8.57 has a slightly smaller unpacked size of 70386 bytes compared to version 0.8.56's 71919 bytes. This reduced footprint could translate to marginal improvements in installation time and resource usage, making it a preferable choice for developers concerned about efficiency.
For developers considering esbuild, both versions represent a powerful tool for streamlining the build process. Esbuild's speed makes it an excellent choice for large projects where build times are a significant bottleneck. The small difference in unpacked size further enhances its appeal. Considering the rapid release cycle, checking the changelog between these versions on the origin repository is recommended to understand the specific fixes and improvements introduced in 0.8.57. However, for most users, upgrading to the newer version is advisable for the latest stability enhancements.
All the vulnerabilities related to the version 0.8.57 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.