Open-source MCP proxy mcp-guard blocks prompt injection before tool calls run
TastePrestigious4419 · reddit · 2026-07-21
The author open-sourced mcp-guard, a lightweight security proxy for MCP servers designed to block indirect prompt injection attacks.
It sits between clients such as Cursor, Claude Desktop, and Claude Code and external MCP servers, intercepting tool requests in real time. The proxy inspects parameters and inputs for injection heuristics, command overrides, and other dangerous payloads, while requiring no code changes and supporting both stdio and HTTP/SSE MCP setups. The post invites the community to test it locally, try to break it, and suggest detection-rule improvements.
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