Esbuild version 0.18.19 represents a minor update to the blazing-fast JavaScript and CSS bundler and minifier, building upon the foundation laid by version 0.18.18. Both versions maintain the same core functionality and MIT license, ensuring consistent performance and licensing terms for developers. The most notable difference lies in the incremented version numbers of the core dependencies. All @esbuild/* packages listed in both dependencies and optionalDependencies are updated from version 0.18.18 to 0.18.19. This suggests that version 0.18.19 includes bug fixes, performance improvements, or potentially new features within the esbuild ecosystem affecting platform-specific binaries. The unpacked size of version 0.18.19 is slightly larger (131272 bytes) compared to version 0.18.18 (131238 bytes), indicating minor code additions or changes. The release date further highlights the recency of version 0.18.19, released shortly after 0.18.18. Developers should consider upgrading to 0.18.19 to benefit from the latest refinements and potential problem resolutions. While the core bundling and minification capabilities remain unchanged, staying updated ensures optimal performance and stability when integrating esbuild into development workflows. Reviewing the changelog for version 0.18.19 is highly recommended to understand the precise nature of the updates within the platform-specific binaries and the reasons for upgrading.
All the vulnerabilities related to the version 0.18.19 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.