Executive brief
Penpot, an open-source design platform for collaborative teams, exposes an unauthenticated WebSocket interface in single-user mode that binds to all network interfaces. Attackers on the same local network can connect to this interface to impersonate the browser plugin, intercept design tasks, and inject forged results, potentially corrupting design work or stealing data.
Technical details
The MCP server plugin WebSocket bridge lacks authentication and listens on all network interfaces in single-user mode, allowing unauthenticated adjacent network access. An attacker can connect to the WebSocket port to spoof the Penpot browser plugin, intercept task payloads between the client and plugin, and return malicious forged results. The vulnerability requires no user interaction and affects versions before 2.18.0.
Affected products
- Penpot Penpot before 2.18.0
Timeline
- 2026-09-27: disclosed