Esbuild versions 0.5.9 and 0.5.10 offer developers an incredibly fast JavaScript bundling and minification solution. Both versions share core characteristics, including the MIT license, which provides flexibility for various projects, and a consistent repository location on GitHub. Developers already familiar with esbuild will find the upgrade straightforward. Analyzing the package metadata reveals subtle shifts. Version 0.5.10 weighs in slightly lighter with an unpacked size of 19532 bytes compared to 0.5.9's 19550 bytes, potentially hinting at minor optimizations or code reductions. Both packages contains 6 files. The most significant difference lies in their release dates; 0.5.10 was published on June 23, 2020, while 0.5.9 appeared on June 22, 2020. This indicates a quick turnaround between releases implying a bug fix or a small feature may have been addressed rapidly. For developers considering esbuild for speeding up their build processes, both versions provide the core functionality described. The choice between the two will probably come down to a desire to use the latest possible version with very minor improvements or a preference/requirement to use a previous stable release of the library, and looking at the changelog to understand changes, fixes and potential breaking changes between versions.
All the vulnerabilities related to the version 0.5.10 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.