MCP connectors cannot point at this AnythingMCP server itself - #882
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A cloud user created an MCP connector with the URL cloud.anythingmcp.com. It imported our own kg_how_to_obtain tool, and every call to it re-entered our /mcp and called itself again: 13,709 calls in two hours on 4 Oct, each held for the 60 s timeout, and everyone's p95 nearly doubled. The MCP client now refuses, before connecting (discovery and calls), a URL whose host is this instance's own SERVER_URL / FRONTEND_URL / CLOUD_PUBLIC_URL host, with a message that says why. Host and port are compared, so another MCP server on the same machine stays allowed on self-hosted instances. Production: 3 such connectors exist; only the looping one was ever called.
keysersoft
enabled auto-merge (squash)
October 5, 2026 11:45
…oop-guard # Conflicts: # packages/backend/src/connectors/engines/mcp-client.engine.spec.ts # packages/backend/src/connectors/engines/mcp-client.engine.ts
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Found in the daily review (5 Oct).
What happened: on 4 Oct a cloud user created an MCP connector "Claude Etsy" with the URL
https://cloud.anythingmcp.com. It imported our ownkg_how_to_obtain, and each call re-entered our/mcpand called the connector again. 13,709 calls in two hours (12–14 UTC), 13,686 of themRequest timed outafter ~60 s each. No outage, but p95 latency for everyone else went from ~600 ms to ~1,100 ms in those hours. This is most of the "Etsy" errors in the weekly report.Fix:
assertNotThisServer()in the MCP client engine, before connecting, for discovery and calls: refuses a URL whose host (with port) is this instance's ownSERVER_URL/FRONTEND_URL/CLOUD_PUBLIC_URL, with a message explaining the loop. Another MCP server on the same machine (e.g.localhost:8080next tolocalhost:4000) and other AnythingMCP instances stay allowed.Production check: 3 MCP connectors point at cloud.anythingmcp.com; only the looping one was ever called (the other two have 0 calls).
Tests: 5 new cases in
mcp-client.engine.spec.ts.