Esbuild, the lightning-fast JavaScript bundler and minifier, saw a minor version bump from 0.8.24 to 0.8.25 in late December 2020. Both versions share the same core description, license (MIT), and repository source, indicating that the fundamental purpose and open-source nature of the tool remained consistent. The core functionality of esbuild as a tool for quickly bundling and minifying JavaScript code for faster website loading times continues to be the primary draw for developers.
However, a closer look reveals subtle differences. Unpacked size increased slightly, from 61507 bytes in version 0.8.24 to 61513 bytes in version 0.8.25, suggesting minor additions or adjustments in the code. The release dates also highlight a relatively quick turnaround between versions, with 0.8.24 released on December 18th and 0.8.25 arriving just two days later on December 20th. This rapid iteration suggests that the update likely addressed a small bug fix or a refinement of existing features rather than a major overhaul.
For developers, this implies a stable and actively maintained tool. While both versions offer excellent performance, upgrading to 0.8.25 is generally recommended to benefit from the latest fixes and optimizations, however small they might be. This continued attention to detail ensures that esbuild remains a reliable choice for optimizing JavaScript code in modern web development workflows, contributing towards a faster and more efficient user experience.
All the vulnerabilities related to the version 0.8.25 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.