The Maginot Line was one of the most sophisticated defensive systems of its time. France built bunkers, artillery positions, tunnels, and obstacles along its eastern frontier. The fortifications were formidable. The problem was not that the wall was weak. The problem was that the attack went around it.
Web3 security often repeats this mistake. Teams concentrate defensive energy on the smart contract while the application around it inherits the ordinary vulnerabilities of the web: compromised frontends, poisoned packages, leaked credentials, insecure APIs, malicious browser extensions, and social engineering.
The contract can be correct while the product is unsafe.
Users do not interact with contracts
Technically, a wallet signs a transaction that invokes onchain programs. Experientially, a person clicks a button on a website. They trust the domain, the interface, the token symbol, the transaction simulation, and the explanation placed beside the action.
That interface can substitute an address. A compromised dependency can alter a transaction before signing. A deceptive approval flow can make a dangerous permission look routine. None of these attacks require breaking the cryptography. They exploit the distance between what the protocol does and what the user believes it is doing.
The attack surface of a decentralised application includes every centralised assumption required to reach it.
Security reviews stop where organisational charts stop
Smart-contract auditors review programs. Frontend teams review interfaces. Infrastructure teams operate deployments. Community teams respond to impersonation and phishing. Each group sees a valid slice of the problem, but attackers are not required to respect those boundaries.
A supply-chain compromise can begin in npm, surface in a deployment pipeline, modify a wallet interaction, and end as an onchain loss. Calling the final event a smart-contract exploit hides the route that made it possible. Calling it a frontend bug understates the economic consequence.
Security needs a system map, not a departmental checklist.
The forgotten perimeter is developer experience
Developers make security decisions through documentation and defaults. If the canonical quickstart hardcodes a sensitive value, skips transaction simulation, or treats error handling as optional, insecure behaviour spreads through copy and paste.
A secure SDK with confusing guidance can produce insecure applications at scale. A slightly more opinionated API—clear network selection, explicit permission scopes, safe transaction construction, and actionable errors—can prevent whole classes of mistakes before an audit begins.
Developer experience is not the soft side of security. It is how security properties survive contact with implementation teams.
AI agents widen the side door
Agentic development adds another actor to the system. An agent can install packages, read documentation, construct transactions, and execute commands faster than a person can review each step. This creates enormous leverage. It also allows one poisoned instruction or overbroad permission to travel farther.
The security model must include tool provenance, secret boundaries, approval points, and evidence of execution. An agent should not inherit every permission available in the developer’s shell merely because that is the easiest environment to build.
If Web3 ignored Web2 because the contract felt like the serious part, it cannot now ignore agent infrastructure because the model feels like a productivity layer. The surrounding system always becomes part of the asset.
Defend the route, not only the destination
A stronger security programme follows the complete journey: source code to dependency graph, dependency graph to build system, build system to deployment, deployment to interface, interface to wallet, wallet to transaction, and transaction to protocol state.
At each transition, ask what identity is trusted, what information can change, what authority is granted, and what evidence remains. Threat modelling becomes less about listing vulnerabilities and more about tracing how a false assumption crosses boundaries.
The goal is not perfect defence. It is to eliminate the unexamined route around the wall.
The wall is still worth building
None of this makes contract security less important. The Maginot Line was not useless because fortifications are useless. It failed as a complete strategy because it protected one interpretation of the battlefield.
Audit the contracts. Verify the cryptography. Test the invariants. Then keep moving outward until the threat model includes the person holding the mouse, the agent holding the shell, and every ordinary system connecting them to the chain.