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Claude Jailbroken to Mint Unlimited Stripe Coupons

We reveal a powerful metadata-spoofing attack that exploits Claude's iMessage integration to mint unlimited Stripe coupons or invoke any MCP tool with arbitrary parameters, without alerting the user.

This attack exploits Claude's inability to verify the true origin of a message received through iMessage: by injecting metadata-like tags into the body of a message, formatted as escaped text that mimics internal server annotations, an attacker can spoof trusted instructions, since Claude interprets everything as plain text without distinguishing between genuine system metadata and user-injected content. Claude Sonnet 4 model Reads formatted message history from iMessage and issues MCP calls to Stripe—all under a single agent instance, without additional middleware or provenance checks. When the iMessage integration is active, a single spoofed SMS can give an attacker command-level access to every tool the user has enabled in Claude (Stripe, GitHub, cloud consoles, file systems, and more).

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