Agentjacking: Poisoned Sentry Errors Hijack Claude Code, Cursor, and Codex via MCP

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Tenet Security and the Cloud Security Alliance disclosed 'Agentjacking,' an attack that injects malicious instructions into Sentry error events using only a public, write-only DSN — which MCP-connected coding agents then retrieve and execute with the developer's own system privileges. Controlled tests hit an ~85% success rate across 100+ orgs, and the chain bypasses EDR, WAF, IAM, and firewalls because every step is technically authorized. Sentry declined a root-cause fix, calling the class 'not defensible' at the platform level — anyone wiring error-tracking MCP servers into an agent should treat ingested events as untrusted input.