Sourced from openzeppelin-solidity's releases.

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 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)

... (truncated)

Sourced from openzeppelin-solidity's changelog.

4.6.0 (2022-04-26)

• 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 royaltyInfo public to allow super call in overrides. (#3305)

Upgradeability notice

• TimelockController: (Action needed) The upgrade from =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.

4.5.0 (2022-02-09)

• 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)

... (truncated)

• d4fb3a8 4.6.0
• 1d9902f Fix update-comment script to ignore invalid tags
• 2cf3ac4 Bump minimum Solidity version for Initializable.sol to 0.8.2 (#3328)
• 24953fb Remove unused constructor argument
• a57bd14 Fix tests on upgradeable contracts after transpilation
• 6096b53 add transpilation guards to the crosschain mocks (#3306)
• ab54fcb make ERC2981:royaltyInfo public (#3305)
• 050180e Fix release script to only release @​openzeppelin/contracts
• 3a2534d 4.6.0-rc.0
• 2a4ca65 Update release script to stop publishing old openzeppelin-solidity package
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