The research team at Koi Security has disclosed a critical vulnerability in Open VSX, the extension marketplace powering VSCode forks like Cursor, Windsurf, Gitpod, VSCodium, and more, collectively used by over 8 million developers.
The vulnerability gave attackers the ability to take full control of the entire marketplace, allowing them to silently push malicious updates to every extension. Any developer with an extension installed could be compromised, no interaction required.
The flaw stemmed from a misconfigured GitHub Actions workflow
The issue was responsibly reported by Koi Security and has since been fixed, though the patching process took considerable time.
Key takeaways:
- One CI misconfiguration exposed full marketplace control
- A malicious update could backdoor thousands of developer environments
- Affected platforms include Cursor, Windsurf, VSCodium, Gitpod, StackBlitz, and more
- Highlights the growing supply chain risk of extension ecosystems
This isn’t just about one marketplace, it’s a broader warning about the privileged, auto-updating nature of software extensions. These extensions often come from third-party developers, run with deep access, and are rarely governed like traditional dependencies.
Full write-up: https://blog.koi.security/marketplace-takeover-how-we-couldve-taken-over-every-developer-using-a-vscode-fork-f0f8cf104d44