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Encrypted prompt injection bypasses Grok guardrails to exfiltrate chat history
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Adversa AI demonstrated a "cryptographic context injection" attack on xAI's Grok that smuggles malicious instructions past guardrail scanners by encrypting them, letting the model decrypt and execute them in its own sandbox.
This attack subverts the standard defense model where input filters inspect content before it reaches the model. Because no content classifier performs cryptographic decryption at inspection time, the technique turns the model's code execution runtime into a trust-laundering mechanism that treats its own decrypted output as trusted.
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The attack places encrypted malicious instructions and a decryption key on a web page, which guardrail scanners pass because they cannot decrypt ciphertext at inspection time.
A proof-of-concept on Grok.com exfiltrated the victim's chat history, username, location, and subscription tier by appending them to a URL as parameters.
xAI acknowledged the report on June 3, 2026, but as of August 19 the technique still worked with no mitigation timeline provided.
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