Esbuild version 0.8.15 represents a minor update to the blazing-fast JavaScript bundler and minifier, following closely on the heels of version 0.8.14. Both versions maintain the same core characteristics: they are licensed under the MIT license, boast an unpacked size of 56336 bytes, and comprise 6 files within the distributed tarball. The key distinction lies in the release date. Version 0.8.15 was published on November 25, 2020, at 09:43:07.013Z, roughly a day after version 0.8.14, which arrived on November 24, 2020, at 06:51:19.984Z.
For developers leveraging esbuild, this small time gap likely signifies bug fixes, performance enhancements, or subtle feature tweaks implemented between the two releases. While the package size and structure remain consistent, upgrading to 0.8.15 is advised to benefit from the most recent improvements and stability refinements made by the esbuild team. As an exceptionally quick bundler and minifier, this library is a valuable tool in optimizing JavaScript projects, improving load times, and streamlining the development workflow. Utilizing the latest version ensures access to the most polished and reliable experience. Remember to always examine the official changelog to fully discover all differences.
All the vulnerabilities related to the version 0.8.15 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.