ERC-721 Standard Violations

Overview

The ERC-721 violations detector identifies NFT contracts that deviate from the ERC-721 standard. Common issues include missing onERC721Received callback in safeTransferFrom, incorrect Transfer event parameters, and missing ERC-165 interface support declaration.

Why This Is an Issue

Non-compliant ERC-721 tokens cause failures in marketplaces, wallets, and bridges that expect standard behavior. Missing safe transfer checks can result in NFTs being permanently locked in contracts that cannot handle them.

Examples

Sample Sigvex Output

{
  "detector_id": "erc721-violations",
  "severity": "low",
  "confidence": 0.88,
  "description": "safeTransferFrom() does not call onERC721Received on the recipient. NFTs transferred to contracts may be permanently locked.",
  "location": { "function": "safeTransferFrom(address,address,uint256)", "offset": 0 }
}

Detection Methodology

Identifies ERC-721 selectors, verifies safe transfer callback implementation, event emissions, and ERC-165 support declarations.

Related Detectors

• ERC-20 Violations
• ERC-165 Spoofing
• Royalty Bypass

References

• EIP-721: Non-Fungible Token Standard
• OpenZeppelin ERC721