Esbuild version 0.12.23 represents a subtle refinement over its predecessor, 0.12.22, in the landscape of JavaScript bundlers and minifiers. While both versions share the core characteristics of being extremely fast and licensed under the permissive MIT license, a closer look reveals nuanced differences. The release of version 0.12.23 on August 26, 2021, a mere five days after 0.12.22, suggests an incremental update, potentially addressing minor bugs or performance tweaks discovered in the earlier release.
Developers considering esbuild will appreciate the package's consistent foundation: it offers remarkably fast bundling and minification, streamlining the build process for web applications. Notably, both versions retain the same file count (6) in their distributed tarballs, but version 0.12.23 unpacks to a slightly larger size (89145 bytes) compared to 0.12.22 (88920 bytes) which means that a few more bytes were added to the code for some improvements. This suggests internal code adjustments or minor feature additions rather than a major overhaul. For most users, the move from 0.12.22 to 0.12.23 should be seamless. Developers prioritizing stability and incremental improvements will find value in adopting the newer version, benefiting from potential bug fixes and optimizations. The consistent repository URL ensures easy access to the source code for those who wish to delve deeper.
All the vulnerabilities related to the version 0.12.23 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.