Cryptographic Context Injection Affects Grok Agents
🛡️ Adversa AI disclosed a technique called Cryptographic Context Injection that caused xAI's Grok web chat (Grok 4.5 Fast) to exfiltrate a user's name, approximate location, subscription tier, and ongoing prompts to an attacker-controlled server during a routine page summary request. The attack packages instructions as ciphertext on a web page, which Grok's Python runtime decrypts and executes, allowing the model to construct a URL embedding private session data and fetch it without user confirmation. Adversa reported the issue to xAI in June 2026, reproduced it on August 19, and advised mitigations for agent harnesses; xAI has not issued a public advisory as of August 20.
