Esbuild versions 0.5.5 and 0.5.4 represent incremental updates to this notably swift JavaScript bundler and minifier. Both versions share identical descriptions, licensing under the MIT license, and repository origins. Notably, both packages maintain the same file count (6) and unpacked size (19309 bytes), hinting at similar feature sets and codebases.
The key difference lies in the release dates. Version 0.5.5 was released on June 20, 2020, while version 0.5.4 was released on June 19, 2020 – a difference of roughly 11 hours. This suggests that version 0.5.5 likely includes bug fixes or minor enhancements addressing issues discovered shortly after the release of 0.5.4. Developers should check the esbuild's changelog or GitHub repository for specific details regarding these updates. While the changes might be small, upgrading to the latest minor version (0.5.5) is generally advisable to benefit from the latest fixes and improvements. Esbuild is an intriguing choice for developers aiming for faster build times in their JavaScript projects. Its speed advantage over other bundlers can significantly reduce development time, especially in larger applications. These rapid updates are valuable to developers seeking a solid and maintained tool.
All the vulnerabilities related to the version 0.5.5 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.