Pattern: Taint-Style Back-End Flaws Are the Dominant MCP Attack Class — Automated Detection Is Catching Up

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The VIPER-MCP research frames MCP vulnerabilities as taint-style flaws: untrusted input flowing from tool arguments into dangerous sinks (shell, SQL, file access) inside the server. Its combined static-and-dynamic analysis found 106 zero-days across ~40K servers, and complementary defenses are appearing — attested tool-server admission with signed clearance assertions, and MCPShield, a graph-neural-network approach for spotting anomalous tool-call traffic. The takeaway for builders: treat MCP server code with the same taint-tracking rigor you'd apply to any web back end.