Why Gasless Onboarding Is a Double-Edged Sword for Security

Paymasters and relayers become centralized choke points. A compromised or malicious relayer can censor, front-run, or drain sponsored transactions. The economic model for relayers is fragile, often subsidized by unsustainable VC grants, leading to centralization risks akin to early Infura dominance.

• Single Point of Failure: A dominant relayer can halt entire dApp ecosystems.
• Economic Attack Vectors: Relayers can be bribed to reorder or drop transactions.
• Opaque Subsidies: User has no visibility into who is paying and why.

Gasless transactions flood public mempools with unfunded intent signatures. This creates a new attack surface for Denial-of-Service (DoS) and signature farming. Adversaries can spam the network with invalid signatures, clogging systems like UniswapX and Across, while harvesting signatures for future replay attacks.

• Mempool Bloat: Free to create, signatures can spam relays, increasing latency for legitimate users.
• Replay Attacks: Harvested signatures can be replayed if a user's nonce management is flawed.
• Systemic Congestion: A targeted attack can cripple intent-based infrastructure.

Mitigation requires shifting from trusted intermediaries to cryptoeconomic security. Solutions like EIP-4337 Bundler competition and SUAVE aim to create a permissionless marketplace for transaction inclusion. The goal is to align incentives so that no single entity controls the flow, similar to MEV-Boost for block building.

• Permissionless Relay: Anyone can become a paymaster/relayer, enforced by smart contracts.
• Staked Security: Relay operators post bonds slashed for malicious behavior.
• Intent Auctions: Users' signed intents are fulfilled via a competitive auction, not a fixed relayer.

Paymasters and relayers become centralized choke points. A dominant service like Gelato or Biconomy can censor transactions or front-run user intents, undermining permissionless access.

• Centralized Failure Point: A single relayer outage halts all gasless activity for dependent dApps.
• MEV Extraction: Relayers can reorder or replicate transactions for maximal extractable value, a risk highlighted by UniswapX's design.

Protocols that sponsor gas open themselves to economic attacks. A malicious actor can spam the network, draining the subsidy pool and creating denial-of-service conditions.

• Costly Spam: Inexpensive actions on L2s can be amplified to incur massive L1 settlement costs for the sponsor.
• Pool Drain: Finite subsidy contracts (e.g., ERC-4337 paymaster staked balances) are explicit financial targets.

Frameworks like UniswapX and CowSwap separate declaration from execution, introducing trusted solver networks. Users trade transaction certainty for better prices, relying on solvers not to exploit their broad intents.

• Solver Collusion: A small set of solvers can manipulate prices or withhold liquidity.
• Execution Risk: The final transaction path is opaque, potentially including unexpected intermediaries or layerzero cross-chain hops.

ERC-4337 smart accounts enable gasless UX but expand the attack surface. A single bug in a widely used account implementation (e.g., Safe{Core} Account Abstraction Kit) or a malicious signature scheme could lead to mass asset compromise.

• Singleton Risk: Ubiquitous smart account code becomes a high-value exploit target.
• Session Key Peril: Convenient 'session keys' for gasless gaming can grant excessive, persistent permissions.