MemGhost attack exploits AI agent persistent memory with 87.5% success rate via legitimate write tools

Short summary

MemGhost is an attack where a hidden instruction in an email or webpage convinces an AI agent to rewrite its own persistent memory — for example, raising a Zelle transfer limit — and that falsified memory persists across all future interactions. It achieves an 87.5% success rate against frontier models by using the agent's own legitimate memory-write tools, bypassing input filters entirely. The fix isn't better prompt filtering but proper authorization boundaries around write actions to persistent state.

• •MemGhost tricks agents into permanently rewriting persistent memory via their own legitimate write tools, achieving 87.5% success on frontier models
• •Input filtering cannot stop this because the exploit uses normal tool calls, not malformed input
• •Fix requires authorization boundaries around memory writes: provenance checks, human-in-the-loop for sensitive fields, and strict write-permission scoping

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