Stored XSS vulnerability in Open VSX Registry: the /vscode/unpkg/{publisher}/{name}/{version}/{path} endpoint serves user-supplied files (HTML, SVG) from within VSIX extension packages with content type deduced from file extension but without Content-Security-Policy, Content-Disposition: attachment, or X-Content-Type-Options: nosniff headers. An attacker registers a publisher account, uploads a VSIX containing a crafted HTML/SVG payload, and induces an authenticated user to visit the resulting URL. The browser renders the file inline in the open-vsx.org origin context, enabling session token exfiltration, PAT generation, and unauthorized publication of malicious extension versions. This constitutes a supply-chain risk since Open VSX extensions are distributed to VS Code, VSCodium, Cursor, Windsurf, and compatible editors.