Tsup is a zero-config TypeScript bundler powered by esbuild, designed for creating modern JavaScript libraries. Version 5.3.0 introduces subtle refinements and improvements over its predecessor, version 5.2.1. While the core functionality remains consistent, examining the package manifests reveals minor adjustments in package sizes and release dates, pointing to internal enhancements and bug fixes.
Developers considering upgrading to 5.3.0 should note the slightly larger unpacked size (2922461 bytes vs 2921542 bytes), hinting at potentially new features or expanded internals. Critically, the dependencies and devDependencies remain identical between the two versions, suggesting no breaking changes or major overhauls to the underlying toolchain. Both versions rely on the same versions of key tools like esbuild, rollup, and TypeScript itself (via peerDependency).
This makes upgrading rather safe, focused primarily on stability and potential performance gains achieved by internal optimizations. The unchanged dependency list helps ensuring compatibility within existing projects. As always, reviewing the official changelog and testing in a controlled environment is recommended before deploying the update in a production environment. The primary advantage comes if you're looking for the most recent bug fixes and any subtle performance improvements within the tsup ecosystem, whilst staying within a familiar and stable environment.
All the vulnerabilities related to the version 5.3.0 of the package
tsup DOM Clobbering vulnerability
A DOM Clobbering vulnerability in tsup v8.3.4 allows attackers to execute arbitrary code via a crafted script in the import.meta.url to document.currentScript in cjs_shims.js components
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.