n8n-MCP: Workflow telemetry sanitizer could retain partial values from URL-shaped node parameters

Summary

In affected versions of n8n-mcp, the workflow telemetry sanitizer could retain partial fragments of URL-shaped node parameters before sending workflow data to the project's anonymous telemetry backend. Values placed in HTTP-Request-style node parameters — such as customer or tenant identifiers, short secrets embedded in query strings, and signed request parameters — could therefore appear in stored telemetry, contrary to the collection boundary documented in PRIVACY.md.

Impact

Operators with access to the project's telemetry backend could read partial fragments of workflow URL parameters that should not have been collected. The bug was scoped to URL-shaped fields in workflow definitions; credentials, OAuth tokens, and workflow execution data are not affected — credentials are removed by a separate code path, and long secrets and known-provider tokens are matched by dedicated patterns.

Patches

Fixed in n8n-mcp 2.51.3. Upgrading is the recommended remediation.

Workarounds

For users who cannot upgrade immediately, disable anonymous telemetry by setting any of these environment variables to true:

• N8N_MCP_TELEMETRY_DISABLED
• TELEMETRY_DISABLED
• DISABLE_TELEMETRY

Credit

Reported by @u-ktdi.