Esbuild versions 0.8.36 and 0.8.37 are both iterations of this incredibly fast JavaScript bundler and minifier, designed to dramatically improve build times for web developers. Both versions share the same core characteristics: they are licensed under MIT, boast a concise file count of six within their distribution, and have an identical unpacked size of 64,262 bytes. This suggests any changes between the versions are focused on internal improvements or bug fixes rather than substantial feature additions that would affect the package size.
The key difference lies in their release dates. Version 0.8.36 was released on January 26, 2021, while version 0.8.37 followed shortly after on January 30, 2021. Given the short timeframe, developers can assume 0.8.37 incorporates bug fixes or minor enhancements identified and addressed quickly after the release of 0.8.36. For developers choosing between these versions, opting for 0.8.37 is advisable to benefit from any stability improvements or refined behavior. This is especially pertinent for projects prioritizing build speed and reliability. While the core functionality remains consistent, the later version provides the most polished experience. The focus remains on efficient bundling and minification making Esbuild a potent tool for optimizing web application performance.
All the vulnerabilities related to the version 0.8.37 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.