Esbuild version 0.7.5 arrived shortly after 0.7.4, offering developers an incremental update to this blazing-fast JavaScript bundler and minifier. Both versions maintain the core promise of esbuild: exceptional speed and efficiency for bundling modern web applications. They share the same MIT license, ensuring a permissive and open use, and boast an identical unpacked size of 38150 bytes across 6 files in their respective tarballs.
The key difference lies in the release date; version 0.7.5 was published on September 24, 2020, roughly a day after 0.7.4's release on September 23, 2020. While the metadata doesn't explicitly detail the specific changes between these closely released versions, the proximity suggests that version 0.7.5 likely addresses bug fixes, minor performance improvements, or urgent security patches identified in 0.7.4. For developers, it's advisable to upgrade to the latest patch version (0.7.5 in this case) when available, as it often delivers a more stable and refined experience. Esbuild continues to offer a compelling alternative to slower bundlers, especially for large projects where build times are critical. Its focus on speed, combined with its easy integration, makes it an attractive choice for modern web development workflows, aiming for optimal performance in web deployments. Both versions leverage the same Git repository managed by Evan Wallace, ensuring a consistent and reliable development source.
All the vulnerabilities related to the version 0.7.5 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.