Esbuild versions 0.8.7 and 0.8.8 represent incremental updates to the popular JavaScript bundler and minifier known for its exceptional speed. Both versions share the same core characteristics: they're licensed under MIT, boast a consistent structure with six files in the distribution, and are maintained within the same GitHub repository, reaffirming their shared lineage and development philosophy focused on performance. While the textual descriptions remain identical, a deeper look reveals subtle, yet potentially significant, differences.
The most apparent change lies in the release date. Version 0.8.8 was released on November 16, 2020, just a few days after version 0.8.7's release on November 13, 2020. This suggests a rapid iteration cycle. The unpacked size also sees a minor increase, going from 50,289 bytes in 0.8.7 to 50,557 bytes in 0.8.8. This suggests some addition or modification of the code, but nothing major.
For developers, this jump indicates that 0.8.8 likely includes bug fixes or minor enhancements implemented in the intervening days. Developers should consider upgrading to 0.8.8 for the latest stability improvements. The consistent file count and shared repository further simplify the upgrade process, mitigating potential compatibility concerns. If you're already leveraging esbuild, moving to 0.8.8 promises a seamless transition with the potential for improved performance.
All the vulnerabilities related to the version 0.8.8 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.