Esbuild, a famously fast JavaScript and CSS bundler and minifier, released version 0.18.9 shortly after version 0.18.8. Analyzing the package data reveals minimal changes between the two releases from a developer's perspective relying solely on this data. Both versions maintain the same core functionality, confirmed by the consistent description and identical repository information, both pointing to the evanw/esbuild GitHub repository. The size of the unpacked library appears to be maintained too, remaining at 130655.
The primary difference lies in the release date and the version numbers of the @esbuild/* dependencies. Version 0.18.9 was released on June 26, 2023, while version 0.18.8 was released on June 25, 2023. All listed dependencies (e.g., @esbuild/linux-x64, @esbuild/darwin-arm64) are bumped from version 0.18.8 to 0.18.9 accordingly. These dependencies seem to be platform-specific binaries or modules necessary for esbuild to function correctly across different operating systems and architectures.
The consistent dependency lists in both "dependencies" and "optionalDependencies" suggests that the core functionality of esbuild remains consistent across these minor versions since it seems that all dependencies versions are updated.
For developers, this likely signifies a bug fix or a minor enhancement release with updated prebuilt binaries. A changelog review is necessary to understand the specifics of the changes, however, the short time frame between releases, coupled with the synchronized version bump of the platform-specific dependencies, emphasizes the importance of staying current with esbuild to benefit from the latest optimizations and stability improvements, and potentially fix some important bugs in specific systems, even if the main functionality remained untouched.
All the vulnerabilities related to the version 0.18.9 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.