Esbuild is a blazing-fast JavaScript bundler and minifier, and versions 0.0.13 and 0.0.14 showcase its rapid development. Both versions maintain the MIT license, ensuring flexibility for developers, and are easily accessible through npm. Examining the metadata reveals that version 0.0.14, released shortly after 0.0.13 on April 7th, 2020, included crucial updates.
A key difference lies in the unpacked size of the package: esbuild 0.0.14 weighs in at 2199 bytes when unpacked, a notable increase from version 0.0.13's 1783 bytes. While seemingly small, this increase within the same day suggests improvements, bug fixes, or expanded features that required additional code.
Developers focused on performance and efficiency in their build processes will find esbuild an attractive option. The small package sizes, even with the increase in 0.0.14, indicate that it remains lightweight despite its bundling and minifying capabilities. This contributes to faster installation and reduces storage overhead. The quick release cycle demonstrates the maintainers are diligently improving esbuild. For developers choosing between these specific versions, testing both could reveal the specific benefits of the increased size in 0.0.14. Each version is available, esbuild 0.0.13 and esbuild 0.0.14, on the npm registry through their respective tarball URLs.
All the vulnerabilities related to the version 0.0.14 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.