Esbuild is a blazing-fast JavaScript bundler and minifier, designed for improved build performance in web development workflows. Comparing versions 0.7.13 and 0.7.12, we observe subtle differences that, while seemingly minor, can be important for developers. The package size in version 0.7.13 is slightly smaller, with an unpacked size of 38776 bytes compared to 38783 bytes in 0.7.12.
A more notable difference lies in the release date, where version 0.7.13 was published on October 8, 2020, at 08:23:48 UTC, while version 0.7.12 was released earlier the same day at 00:56:10 UTC. This suggests that version 0.7.13 likely addresses bug fixes or minor improvements identified shortly after the release of 0.7.12.
For developers choosing between these versions, opting for 0.7.13 is advisable due to its slightly smaller footprint and the potential inclusion of immediate fixes. However, the core functionality and features remain consistent between the two versions, both offering Esbuild's signature speed and efficiency in bundling and minifying JavaScript code. Leveraging Esbuild in your projects can significantly reduce build times, enhancing developer productivity and potentially improving website performance.
All the vulnerabilities related to the version 0.7.13 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.