Impact Upgradeable contracts using "UUPSUpgradeable" may be vulnerable to an attack affecting uninitialized implementation contracts. We will update this advisory with more information soon. Patches A fix is included in version 4.3.2 of "@openzeppelin/contracts" and "@openzeppelin/contracts-upgradeable". Workarounds Initialize implementation contracts using "UUPSUpgradeable" by invoking the initializer function (usually called "initialize"). An example is provided "in the forum" (https://forum.openzeppelin.com/t/security-advisory-initialize-uups-implementation-contracts/15301). References A post-mortem will be published in a few days in the "OpenZeppelin Forum" (https://forum.openzeppelin.com/). For more information If you have any questions or comments about this advisory, or need assistance executing the mitigation, email us at security@openzeppelin.com.