Esbuild is a popular JavaScript bundler and minifier known for its exceptional speed. Comparing versions 0.6.26 and 0.6.27 reveals subtle but important differences for developers. Both versions share the same core characteristics: they're distributed under the MIT license, boast a concise file count of 6 with an unpacked size of 32114 bytes, and are accessible via the same GitHub repository.
The primary distinction lies in their release dates. Version 0.6.26 was released on August 18, 2020, while version 0.6.27 followed shortly after on August 21, 2020. This three-day gap suggests that version 0.6.27 likely contains bug fixes, performance improvements, or minor feature additions that were deemed necessary after the initial 0.6.26 release.
For developers considering esbuild, choosing the latest version, 0.6.27, is recommended. This ensures they benefit from the most up-to-date optimizations and resolutions, contributing to a smoother development experience. Although the specific changes between these versions aren't detailed in the provided data, the rapid succession of releases implies enhancements that could positively impact bundling speed, code minification, and overall efficiency. Therefore, staying current with the newest stable version of esbuild is generally a best practice for maximizing its advantages in a JavaScript project.
All the vulnerabilities related to the version 0.6.27 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.