# IERC20Base Noncompliant With ERC20 Standard Low/Info · Three Sigma · Hybrid orderbook DEX · 3rd April 2024 Finding 3S-Vertex-N01 of the Vertex security review. - Report: /reports/vertex - Source: https://github.com/0xsimao/audits/blob/main/Three%20Sigma/2024-04-03-vertex.pdf --- ### Description The interface declares [increaseAllowance and decreaseAllowance](https://github.com/vertex-protocol/vertex-contracts-3sigma-audit/blob/50601071fb44010524ce4d667c5c881af1b2533e/contracts/interfaces/IERC20Base.sol#L31-L37) functions, which aren't part of the official [ERC20](https://eips.ethereum.org/EIPS/eip-20) standard. Calls to such functions may revert with some tokens. However, these functions are part of the [OpenZeppelin's ERC20 implementation](https://docs.openzeppelin.com/contracts/2.x/api/token/erc20#ERC20) designed to mitigate well-known issues around setting allowances. It's important to note that these functions do not entirely fix these issues. An [example](https://github.com/d-xo/weird-erc20?tab=readme-ov-file#approval-race-protections) is USDT and its "approval race protection," which causes other issues. Additionally, the decimals() function is optional, and contracts mustn't rely on it. ### Recommendation It's advisable to use [OpenZeppelin's SafeERC20 lib](https://docs.openzeppelin.com/contracts/2.x/api/token/erc20#SafeERC20), not only for dealing with allowances but also with transfers, without reinventing the wheel, as seen in ERC20Helper.sol. ### Status Acknowledged Disclosed by 0xSimao (https://0xsimao.com/). --- Related findings: - [Throughout code base, implement using SafeERC20 for IERC20 for better readability](https://0xsimao.com/findings/fuji-finance-erc20-ierc20-better-readability): Fuji Finance - [decimals() is not part of the ERC20 standard and not all tokens may implement it as expected, which may cause initialize() to fail](https://0xsimao.com/findings/mitosis-decimals-part-erc20-initialize): Mitosis