Esbuild 0.18.0 introduces a minor version bump, succeeding version 0.17.19, both powerful JavaScript and CSS bundlers praised for their exceptional speed. The core functionality remains consistent, indicated by the unchanged description and license (MIT). Both versions share the same repository URL, confirming they derive from the same project source.
The primary difference lies in the updated versions of the platform-specific binary packages listed in dependencies and optionalDependencies. While both include a comprehensive set of binaries for various operating systems and architectures (Linux, Windows, macOS, Android, FreeBSD, etc.), version 0.18.0 upgrades these to their corresponding 0.18.0 versions, replacing the previous 0.17.19 counterparts. This suggests the update primarily focuses on improvements, bug fixes, or compatibility updates within the pre-compiled binaries themselves for each platform. Developers leveraging esbuild across diverse environments should consider this upgrade to benefit from platform-specific enhancements.
The dist section reveals a slight increase in unpackedSize from 130127 bytes in 0.17.19 to 130436 bytes in 0.18.0. This minor increase further suggests internal code changes or additions within the binaries. Finally, the releaseDate confirms that version 0.18.0 was published on June 9, 2023, subsequent to version 0.17.19 which released on May 13, 2023. Developers should upgrade to the latest version to get the benefits of the latest bug fixes and improvements that are delivered with the new binaries.
All the vulnerabilities related to the version 0.18.0 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.