Esbuild, a renowned JavaScript and CSS bundler and minifier, has recently released version 0.21.5, succeeding the previous stable version 0.21.4. Both versions maintain the core promise of extreme speed and efficiency, appealing to developers seeking to optimize their build processes. The description and the repository details remain consistent, emphasizing the project's continued commitment to its established goals. The number of files and unpacked file size after installation are the same.
A notable difference lies in the releaseDate. Version 0.21.5 was released on June 9th, 2024, while version 0.21.4 was released on May 25th, 2024. This three week gap suggests that v0.21.5 incorporates bug fixes, performance improvements, or minor feature enhancements developed since the previous release. For developers, upgrading to the latest version is generally recommended to benefit from these improvements and ensure compatibility with the latest tools and standards.
The optionalDependencies section lists prebuilt binaries for various platforms, ensuring esbuild's cross-platform compatibility. Each optional dependency is updated which suggests that these binaries were re-compiled for this particular version. Developers targeting specific operating systems or architectures should take note of these dependencies to ensure esbuild functions optimally in their environment.
Given the relatively short time between releases, developers can expect a smooth transition when upgrading from 0.21.4 to 0.21.5. Reviewing the official changelog or release notes will provide detailed information about specific changes and potential breaking changes. As always verifying that your projects doesn't break is something users should do.
All the vulnerabilities related to the version 0.21.5 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.