Esbuild version 0.7.3 represents a minor update to the popular JavaScript bundler and minifier, building upon the foundation laid by version 0.7.2. Both versions maintain the core promise of esbuild: extremely fast bundling and minification, making it a compelling choice for developers seeking to optimize their build processes. Both are released with an MIT license ensuring flexibility for various project types.
Looking at the metadata reveals differences, while seemingly identical in file count (6), unpackedSize of version 0.7.3 grew to 38316 from the 37430 of the 0.7.2, indicating internal changes (bug fixes, performance tweaks, or new features) that contribute to a slightly larger footprint. Crucially, version 0.7.3 emerged on 2020-09-23, a few days after 0.7.2 (2020-09-19), suggesting a rapid response to potential issues or the inclusion of last-minute improvements.
For developers, this means opting for version 0.7.3 offers the advantage of potentially benefiting from those fixes and enhancements. If performance is a key priority, checking esbuild's changelog for 0.7.3 is recommended to identify and leverage any specific speed improvements implemented in this release. Considering how fast is Esbuild compared with other alternatives, even a small fix or improvement translates and gives impactful gains. While both are viable, the subtle differences suggest 0.7.3 is possibly the preferred choice for new projects or upgrades seeking the most up-to-date refinements.
All the vulnerabilities related to the version 0.7.3 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.