Skill Issues: How We Discovered Supply Chain Attack Vectors in an AI Agent Skills Marketplace
Orca Security's research team discovered four supply chain attack primitives in a prominent AI agent skills marketplace (where developers install reusable prompt-based extensions for AI coding agents). The primitives include: (1) install count inflation — unauthenticated GET requests can trivially spoof popularity metrics; (2) non-deterministic security scanning — skills are scanned only at creation and again only when they become popular, creating a window for malicious modifications; (3) silent skill override — installing a skill with the same name as an existing one silently replaces it with no warning; and (4) no fine-grained updates — the update command refreshes all installed skills at once with no diff or changelog. The researchers demonstrated three end-to-end attack flows (bait-and-switch, nested skill injection, and delayed weaponization via update) that achieved persistent code execution through malicious skills that passed the platform's security audits. Real-world testing confirmed actual code execution on end-user systems. The post provides mitigation guidance for users (audit skills manually, avoid blind updates, be suspicious of name collisions, pin versions where possible) and for platform operators (authenticate telemetry, implement continuous scanning, warn on name collisions, support fine-grained auditable updates).
https://orca.security/resources/blog/ai-agent-skill-supply-chain-security
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