v4.6.0

• crosschain: Add a new set of contracts for cross-chain applications. CrossChainEnabled is a base contract with instantiations for several chains and bridges, and AccessControlCrossChain is an extension of access control that allows cross-chain operation. (#3183)
• AccessControl: add a virtual _checkRole(bytes32) function that can be overridden to alter the onlyRole modifier behavior. (#3137)
• EnumerableMap: add new AddressToUintMap map type. (#3150)
• EnumerableMap: add new Bytes32ToBytes32Map map type. (#3192)
• ERC20FlashMint: support infinite allowance when paying back a flash loan. (#3226)
• ERC20Wrapper: the decimals() function now tries to fetch the value from the underlying token instance. If that calls revert, then the default value is used. (#3259)
• draft-ERC20Permit: replace immutable with constant for _PERMIT_TYPEHASH since the keccak256 of string literals is treated specially and the hash is evaluated at compile time. (#3196)
• ERC1155: Add a _afterTokenTransfer hook for improved extensibility. (#3166)
• ERC1155URIStorage: add a new extension that implements a _setURI behavior similar to ERC721's _setTokenURI. (#3210)
• DoubleEndedQueue: a new data structure that supports efficient push and pop to both front and back, useful for FIFO and LIFO queues. (#3153)
• Governor: improved security of onlyGovernance modifier when using an external executor contract (e.g. a timelock) that can operate without necessarily going through the governance protocol. (#3147)
• Governor: Add a way to parameterize votes. This can be used to implement voting systems such as fractionalized voting, ERC721 based voting, or any number of other systems. The params argument added to _countVote method, and included in the newly added _getVotes method, can be used by counting and voting modules respectively for such purposes. (#3043)
• Governor: rewording of revert reason for consistency. (#3275)
• Governor: fix an inconsistency in data locations that could lead to invalid bytecode being produced. (#3295)
• Governor: Implement IERC721Receiver and IERC1155Receiver to improve token custody by governors. (#3230)
• TimelockController: Implement IERC721Receiver and IERC1155Receiver to improve token custody by timelocks. (#3230)
• TimelockController: Add a separate canceller role for the ability to cancel. (#3165)
• Initializable: add a reinitializer modifier that enables the initialization of new modules, added to already initialized contracts through upgradeability. (#3232)
• Initializable: add an Initialized event that tracks initialized version numbers. (#3294)
• ERC2981: make royaltiInfo public to allow super call in overrides. (#3305)

Upgradeability notice

• TimelockController: (Action needed) The upgrade from <4.6 to >=4.6 introduces a new CANCELLER_ROLE that requires set up to be assignable. After the upgrade, only addresses with this role will have the ability to cancel. Proposers will no longer be able to cancel. Assigning cancellers can be done by an admin (including the timelock itself) once the role admin is set up. To do this, we recommend upgrading to the TimelockControllerWith46MigrationUpgradeable contract and then calling the migrateTo46 function.

Breaking changes

• Governor: Adds internal virtual _getVotes method that must be implemented; this is a breaking change for existing concrete extensions to Governor. To fix this on an existing voting module extension, rename getVotes to _getVotes and add a bytes memory argument. (#3043)
• Governor: Adds params parameter to internal virtual _countVote method; this is a breaking change for existing concrete extensions to Governor. To fix this on an existing counting module extension, add a bytes memory argument to _countVote. (#3043)
• Governor: Does not emit VoteCast event when params data is non-empty; instead emits VoteCastWithParams event. To fix this on an integration that consumes the VoteCast event, also fetch/monitor VoteCastWithParams events. (#3043)
• Votes: The internal virtual function _getVotingUnits was made view (which was accidentally missing). Any overrides should now be updated so they are view as well.

v4.6.0-rc.0

This prerelease is now available for open review! Let us know your feedback and if you find any security issues.

We have a bug bounty with rewards of up to USD $25,000 and a special POAP for submitting a valid issue.

See the announcement for some more details.

v4.5.0

• ERC2981: add implementation of the royalty standard, and the respective extensions for ERC721 and ERC1155. (#3012)
• GovernorTimelockControl: improve the state() function to have it reflect cases where a proposal has been canceled directly on the timelock. (#2977)
• Preset contracts are now deprecated in favor of Contracts Wizard. (#2986)
• Governor: add a relay function to help recover assets sent to a governor that is not its own executor (e.g. when using a timelock). (#2926)
• GovernorPreventLateQuorum: add new module to ensure a minimum voting duration is available after the quorum is reached. (#2973)
• ERC721: improved revert reason when transferring from wrong owner. (#2975)
• Votes: Added a base contract for vote tracking with delegation. (#2944)
• ERC721Votes: Added an extension of ERC721 enabled with vote tracking and delegation. (#2944)
• ERC2771Context: use immutable storage to store the forwarder address, no longer an issue since Solidity >=0.8.8 allows reading immutable variables in the constructor. (#2917)
• Base64: add a library to parse bytes into base64 strings using encode(bytes memory) function, and provide examples to show how to use to build URL-safe tokenURIs. (#2884)
• ERC20: reduce allowance before triggering transfer. (#3056)
• ERC20: do not update allowance on transferFrom when allowance is type(uint256).max. (#3085)
• ERC20: add a _spendAllowance internal function. (#3170)
• ERC20Burnable: do not update allowance on burnFrom when allowance is type(uint256).max. (#3170)
• ERC777: do not update allowance on transferFrom when allowance is type(uint256).max. (#3085)
• ERC777: add a _spendAllowance internal function. (#3170)
• SignedMath: a new signed version of the Math library with max, min, and average. (#2686)
• SignedMath: add a abs(int256) method that returns the unsigned absolute value of a signed value. (#2984)
• ERC1967Upgrade: Refactor the secure upgrade to use ERC1822 instead of the previous rollback mechanism. This reduces code complexity and attack surface with similar security guarantees. (#3021)
• UUPSUpgradeable: Add ERC1822 compliance to support the updated secure upgrade mechanism. (#3021)
• Some more functions have been made virtual to customize them via overrides. In many cases this will not imply that other functions in the contract will automatically adapt to the overridden definitions. People who wish to override should consult the source code to understand the impact and if they need to override any additional functions to achieve the desired behavior.

Breaking changes

• ERC1967Upgrade: The function _upgradeToAndCallSecure was renamed to _upgradeToAndCallUUPS, along with the change in security mechanism described above.
• Address: The Solidity pragma is increased from ^0.8.0 to ^0.8.1. This is required by the account.code.length syntax that replaces inline assembly. This may require users to bump their compiler version from 0.8.0 to 0.8.1 or later. Note that other parts of the code already include stricter requirements.

v4.5.0-rc.0

This prerelease is now available for review! Let us know your feedback and if you find any security issues.

We have a bug bounty with rewards of up to USD $25,000 and a special POAP for submitting a valid issue.

See the announcement for some more details.

v4.4.2

⚠️ This is a patch for a medium severity issue. For more information visit the security advisory.

• GovernorCompatibilityBravo: Fix error in the encoding of calldata for proposals submitted through the compatibility interface with explicit signatures. (#3100)

v4.4.1

⚠️ This is a patch for a low severity vulnerability. For more information visit the security advisory.

• Initializable: change the existing initializer modifier and add a new onlyInitializing modifier to prevent reentrancy risk. (#3006)

Breaking change

It is no longer possible to call an initializer-protected function from within another initializer function outside the context of a constructor. Projects using OpenZeppelin upgradeable proxies should continue to work as is, since in the common case the initializer is invoked in the constructor directly. If this is not the case for you, the suggested change is to use the new onlyInitializing modifier in the following way:

 contract A {
-    function initialize() public   initializer { ... }
+    function initialize() internal onlyInitializing { ... }
 }
 contract B is A {
     function initialize() public initializer {
         A.initialize();
     }
 }

v4.4.0

Check out the first OpenZeppelin Community Call where the team discussed everything that is included in this release.

And if you missed it, we recently announced an official bug bounty program for OpenZeppelin Contracts. Check it out!

• Ownable: add an internal _transferOwnership(address). (#2568)
• AccessControl: add internal _grantRole(bytes32,address) and _revokeRole(bytes32,address). (#2568)
• AccessControl: mark _setupRole(bytes32,address) as deprecated in favor of _grantRole(bytes32,address). (#2568)
• AccessControlEnumerable: hook into _grantRole(bytes32,address) and _revokeRole(bytes32,address). (#2946)
• EIP712: cache address(this) to immutable storage to avoid potential issues if a vanilla contract is used in a delegatecall context. (#2852)
• Add internal _setApprovalForAll to ERC721 and ERC1155. (#2834)
• Governor: shift vote start and end by one block to better match Compound's GovernorBravo and prevent voting at the Governor level if the voting snapshot is not ready. (#2892)
• GovernorCompatibilityBravo: consider quorum an inclusive rather than exclusive minimum to match Compound's GovernorBravo. (#2974)
• GovernorSettings: a new governor module that manages voting settings updatable through governance actions. (#2904)
• PaymentSplitter: now supports ERC20 assets in addition to Ether. (#2858)
• ECDSA: add a variant of toEthSignedMessageHash for arbitrary length message hashing. (#2865)
• MerkleProof: add a processProof function that returns the rebuilt root hash given a leaf and a proof. (#2841)
• VestingWallet: new contract that handles the vesting of Ether and ERC20 tokens following a customizable vesting schedule. (#2748)
• Governor: enable receiving Ether when a Timelock contract is not used. (#2748)
• GovernorTimelockCompound: fix ability to use Ether stored in the Timelock contract. (#2748)

v4.3.3

⚠️ This is a security patch. For more information visit the security advisory.

• ERC1155Supply: Handle totalSupply changes by hooking into _beforeTokenTransfer to ensure consistency of balances and supply during IERC1155Receiver.onERC1155Received calls.

v4.3.2

⚠️ This is a security patch. For more information visit the security advisory.

• UUPSUpgradeable: Add modifiers to prevent upgradeTo and upgradeToAndCall being executed on any contract that is not the active ERC1967 proxy. This prevents these functions being called on implementation contracts or minimal ERC1167 clones, in particular.

v4.3.1

⚠️ This is a security patch. For more information visit the security advisory.

• TimelockController: Add additional isOperationReady check.