Yu Xian, the founder of SlowMist, posted on Twitter, "We have received feedback from many people since last night that the ARB that they had obtained with great difficulty was stolen. This is one of the reasons: the scammers built an upgradeable DEX router and lured users to approve the router for token swaps through early publicity. When users applied for the ARB airdrop and exchanged it for approved tokens, the router owner stole the user's previously approved tokens through contract upgrades."