![]() ![]() Several Token contracts added redundant checks in standard approve(), requiring that the approved _amount smaller or equal to the current balance. After upgrading Solidity compiler to 0.4.22, incompatibilities would arise and these contracts could not perform normal transactions on decentralized exchanges (DEX) or DApp in most cases, whereas a majority of DApp developing teams were off guard and unaware of such a problem. #ERC 20 TOKENS LIST CODE#Thousands of deployed Token contracts referred to incorrect example code on Ethereum official website and OpenZeppelin, resulting in several functions failing to meet ERC20 standard. Lots of ERC20 token contracts do not follow the ERC20 standard strictly, which is troublesome to developers of DApps on ERC20 tokens. Failure of Satisfying Specification in Many ERC20 contracts ![]() We have revealed more than 800 contracts with the same problem after scanning over 20,000 contracts deployed on Etherscan. After further analysis, we caught this bug in at least 81 contracts. On May 20th, 2018, a critical logical flaw was found in EDU along with other three Token contracts (CVE-2018–11397, CVE-2018–11398), causing that users' balances could be transferred out randomly. There is one other contract at least containing this problem. Hackers minted and dumped a tremendous amount of tokens, resulting in SMT's collapse. On April 25th, 2018, a similar integer overflow got uncovered in SMT. There are 10 other contracts at least containing this problem. On April 22th, 2018, the attack on Beaut圜hain(BEC) contract hardly decreased the token price to zero via pouring astronomical tokens to exchanges through an integer overflow. On June 18th, 2016, the DAO hack caused a total loss of over 3,600,000 ethers(ETH) worth over a billion dollars, and the Ethereum hard-fork afterwards led to the Ethereum community breaking apart. Lots of critical security issues have been revealed, some of which have led to severe financial losses for developers, investors, even Ethereum community as well. Here is a daily trend chart of ERC20 contracts created according to our statistics:ĮRC20 Token specification has gone through challenges and improvements during its growth. As of June 26th, 2018, more than 95,000 ERC20 token smart contracts have been deployed according to statistics from Etherscan.
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