Esbuild versions 0.1.0 and 0.1.1 represent very early iterations of this remarkably fast JavaScript bundler and minifier. Both versions share the same core promise: to provide developers with an exceptionally speedy build process. Described as "extremely fast," esbuild aims to significantly reduce build times compared to more traditional bundlers. They are released under the MIT license, making them free to use and modify.
Both releases appear structurally identical in terms of repository location (GitHub), the number of files included in the package (3), and even the unpacked size (2462). This suggests that the changes between versions 0.1.0 and 0.1.1 were likely focused on internal improvements, bug fixes, or minor feature enhancements rather than substantial architectural alterations or the addition of major new capabilities.
The most noticeable distinction is the release date. Version 0.1.1 was published approximately five hours after version 0.1.0. For developers, this indicates a rapid development pace and responsiveness from the esbuild team in its early stages. It's likely that 0.1.1 addresses some immediate issues or refinements identified shortly after the initial 0.1.0 release. While the detailed changelog isn't provided, considering the minimal time gap, updating to 0.1.1 would be advisable to benefit from any potential quick fixes or optimizations made available by the developers.
All the vulnerabilities related to the version 0.1.1 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.