As blockchain technology expands, onchain agents powered by AI and smart protocols like x402 and ERC-8004 are becoming increasingly prevalent. These agents autonomously manage transactions, interact with smart contracts, and facilitate decentralized applications (dApps) operations. While onchain agents promise greater efficiency and automation, they also introduce new and complex security threats that require urgent attention.

Onchain agents operate based on permissions and smart contract instructions, but improperly scoped permissions can create vulnerabilities. If these agents have excessive access rights, attackers can exploit them to drain user assets or manipulate contract logic. Strict permission scoping and role-based access control (RBAC) are essential to minimize these risks by limiting agents' capabilities to only what is necessary.

Malicious plugins or code injections are a significant threat vector. Attackers may introduce harmful plugins that override legitimate functions or poison data inputs, causing agents to execute unauthorized actions. Techniques like function override attacks and cross-protocol calls can exploit agents to spread malicious instructions across multiple smart contracts or external services, expanding the attack surface

While detailed public information on x402 and ERC-8004 is limited, they are part of emerging standards for onchain agent interactions and automation. Such protocols typically rely on model context protocols (MCP) for behavior control, which adds flexibility but also security complexity.

For x402 and ERC-8004 agents, unchecked plugin integrations or input manipulations during runtime interaction phases (as opposed to model training phases) could lead to critical issues like private key leaks, unauthorized fund transfers, or system logic corruption. Due to the public and immutable nature of blockchain, any exploitation can cause irreversible losses.

To defend against these security threats, developers need to enforce strict plugin verification, sanitize all inputs, and apply least privilege principles consistently. Multi-signature transaction approvals and real-time transaction simulations can add additional safety layers by preventing reckless or malicious agent actions.

Continuous monitoring and dynamic threat detection are crucial to identify suspicious agent behavior or interacting contracts. Furthermore, ensuring address validation and risk assessments for tokens can help agents avoid scams like rug pulls or impersonating tokens.

Designing onchain agents with trust, intent verification, and controlled access upfront — rather than as afterthoughts — is critical to safeguarding crypto assets and maintaining user confidence in emerging blockchain AI solutions.