Esbuild, a lightning-fast JavaScript bundler and minifier, released version 0.7.16 on October 16, 2020, as a minor update following version 0.7.15, which was released on October 13, 2020. Both versions maintain the same MIT license and originate from the same GitHub repository managed by evanw. While the core description of the package remains consistent, emphasizing its speed and bundling/minification capabilities, several subtle differences exist.
The most noticeable change is the unpacked size of the package, with version 0.7.16 increasing to 39014 bytes from 38776 bytes in the previous version. This slight increase in size suggests the inclusion of new features, bug fixes, or performance improvements within the newer release. While the file count remains the same at 6, developers should be aware that even minor version bumps can introduce changes impacting build processes or runtime behavior, and the newer version will have those minor changes.
For developers considering esbuild, the key takeaway is its commitment to speed and efficiency. These versions offer a reliable solution for bundling and minifying JavaScript code, contributing to faster website load times and improved user experiences. While the specific changes between 0.7.15 and 0.7.16 aren't explicitly detailed in the provided data, the release date proximity suggests these are likely incremental improvements focused on refining the existing functionality. Reviewing the changelog on the esbuild GitHub repository is recommended for a comprehensive understanding of the exact modifications made in version 0.7.16.
All the vulnerabilities related to the version 0.7.16 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.