Coding agents install deprecated MCP servers from stale training data, research finds
Arindam_1729 · x · 2026-11-06
Glow Labs reviewed real coding agent sessions and identified a pattern dubbed mcphantom: agents installing deprecated MCP servers on developer machines.
Key findings:
- In 98% of affected sessions, the package name came from the model's training data rather than any live check of what's maintained; the other 2% came from users typing the old name themselves.
- Asked for "a github mcp", agents often pick an early Anthropic reference server remembered from training instead of the official GitHub one. That repo was archived in May 2025 with no security updates, and maintainers closed an RCE report as out of scope.
- Four high-severity vulnerabilities were found across the old reference servers, including remote code execution in the puppeteer one; the packages accumulated 17.3 million npm downloads since July.
In short, agents are installing software that will never get patched — MCP server selection deserves a security review.
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