Esbuild version 0.4.13 marks a minor iteration in this exceptionally fast JavaScript bundler and minifier, building upon the foundation laid by version 0.4.12. Both versions share the same core description, license (MIT), and repository details, indicating a continued commitment to open-source principles and ongoing development by Evan Wallace. The distribution information reveals that both versions maintain the same file count (6) and unpacked size (20806 bytes), suggesting that the changes between these releases likely involve internal code optimizations, bug fixes, or subtle feature enhancements rather than significant alterations to the overall package structure or size.
The most notable difference lies in the release date. Version 0.4.13 was published on June 9, 2020, at 20:45:12.799Z, approximately 19 hours after version 0.4.12, which was released on the same day at 01:01:17.290Z. This relatively short time gap between releases suggests that 0.4.13 might address a critical bug or issue discovered shortly after the initial release of 0.4.12.
For developers using esbuild, upgrading from 0.4.12 to 0.4.13 is recommended to ensure they are running the most stable and up-to-date version, potentially benefiting from any fixes or improvements incorporated in the newer release.While the changelog isn't provided here, investigating the project's GitHub repository for release notes associated with version 0.4.13 would provide a more detailed understanding of the specific changes implemented. Esbuild's speed is still a key selling point, making it an attractive choice for projects where build performance is critical.
All the vulnerabilities related to the version 0.4.13 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.