Esbuild versions 0.6.28 and 0.6.29 are both iterations of the blazingly fast JavaScript bundler and minifier that provides an alternative to heavier tools like Webpack and Parcel. Both versions maintain the core functionalities that developers rely on for efficient code transformation, as evidenced by their identical descriptions, MIT license, Git repository, file count (6), and unpacked size (31204 bytes). This suggests a focus on under-the-hood improvements rather than groundbreaking feature additions.
The key differentiator lies in their release dates. Version 0.6.29 was published on September 2nd, 2020, while version 0.6.28 was released on August 27th, 2020. The short interval between releases indicates a patch or minor update focused on bug fixes, performance enhancements, or addressing compatibility issues discovered in the preceding version. Developers should upgrade to version 0.6.29 for the most stable and optimized experience. These incremental updates are crucial for maintaining the performance edge esbuild offers, ensuring faster build times and smaller bundle sizes. While specific changes aren't detailed in the metadata, the update signifies a commitment to continuous improvement, making esbuild a reliable choice for developers seeking rapid JavaScript bundling and minification. Regular upgrades are advisable to leverage these enhancements for optimal development workflows.
All the vulnerabilities related to the version 0.6.29 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.