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.

v3.4.2-solc-0.7

• TimelockController: Add additional isOperationReady check.

v3.4.2

• TimelockController: Add additional isOperationReady check.

v4.3.0

Visit our blog for the full 4.3 announcement as well as Governor announcement!

• ERC2771Context: use private variable from storage to store the forwarder address. Fixes issues where _msgSender() was not callable from constructors. (#2754)
• EnumerableSet: add values() functions that returns an array containing all values in a single call. (#2768)
• Governor: added a modular system of Governor contracts based on GovernorAlpha and GovernorBravo. (#2672)
• Add an interfaces folder containing solidity interfaces to final ERCs. (#2517)
• ECDSA: add tryRecover functions that will not throw if the signature is invalid, and will return an error flag instead. (#2661)
• SignatureChecker: Reduce gas usage of the isValidSignatureNow function for the "signature by EOA" case. (#2661)

v4.2.0

Read the full announcement in the blog!

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• ERC20Votes: add a new extension of the ERC20 token with support for voting snapshots and delegation. (#2632)
• ERC20VotesComp: Variant of ERC20Votes that is compatible with Compound's Comp token interface but restricts supply to uint96. (#2706)
• ERC20Wrapper: add a new extension of the ERC20 token which wraps an underlying token. Deposit and withdraw guarantee that the total supply is backed by a corresponding amount of underlying token. (#2633)
• Enumerables: Improve gas cost of removal in EnumerableSet and EnumerableMap.
• Enumerables: Improve gas cost of lookup in EnumerableSet and EnumerableMap.
• Counter: add a reset method. (#2678)
• Tokens: Wrap definitely safe subtractions in unchecked blocks.
• Math: Add a ceilDiv method for performing ceiling division.
• ERC1155Supply: add a new ERC1155 extension that keeps track of the totalSupply of each tokenId. (#2593)
• BitMaps: add a new BitMaps library that provides a storage efficient datastructure for uint256 to bool mapping with contiguous keys. (#2710)

Breaking Changes

• ERC20FlashMint is no longer a Draft ERC. (#2673))

How to update: Change your import paths by removing the draft- prefix from @openzeppelin/contracts/token/ERC20/extensions/draft-ERC20FlashMint.sol.

See Releases and Stability: Drafts.

v4.1.0

Read the full announcement in the blog or check out the changelog.

• IERC20Metadata: add a new extended interface that includes the optional name(), symbol() and decimals() functions. (#2561)
• ERC777: make reception acquirement optional in _mint. (#2552)
• ERC20Permit: add a _useNonce to enable further usage of ERC712 signatures. (#2565)
• ERC20FlashMint: add an implementation of the ERC3156 extension for flash-minting ERC20 tokens. (#2543)
• SignatureChecker: add a signature verification library that supports both EOA and ERC1271 compliant contracts as signers. (#2532)
• Multicall: add abstract contract with multicall(bytes[] calldata data) function to bundle multiple calls together (#2608)
• ECDSA: add support for ERC2098 short-signatures. (#2582)
• AccessControl: add a onlyRole modifier to restrict specific function to callers bearing a specific role. (#2609)
• StorageSlot: add a library for reading and writing primitive types to specific storage slots. (#2542)
• UUPS Proxies: add UUPSUpgradeable to implement the UUPS proxy pattern together with EIP1967Proxy. (#2542)

v4.0.0

Read the full announcement in the blog or check out the changelog.

Note: Upgradeable contracts using OpenZeppelin Contracts 3.x cannot upgrade to 4.x.

Changelog

• Now targeting the 0.8.x line of Solidity compilers. For 0.6.x (resp 0.7.x) support, use version 3.4.0 (resp 3.4.0-solc-0.7) of OpenZeppelin.
• Context: making _msgData return bytes calldata instead of bytes memory (#2492)
• ERC20: removed the _setDecimals function and the storage slot associated to decimals. (#2502)
• Strings: addition of a toHexString function. (#2504)
• EnumerableMap: change implementation to optimize for key → value lookups instead of enumeration. (#2518)
• GSN: deprecate GSNv1 support in favor of upcoming support for GSNv2. (#2521)
• ERC165: remove uses of storage in the base ERC165 implementation. ERC165 based contracts now use storage-less virtual functions. Old behavior remains available in the ERC165Storage extension. (#2505)
• Initializable: make initializer check stricter during construction. (#2531)
• ERC721: remove enumerability of tokens from the base implementation. This feature is now provided separately through the ERC721Enumerable extension. (#2511)
• AccessControl: removed enumerability by default for a more lightweight contract. It is now opt-in through AccessControlEnumerable. (#2512)
• Meta Transactions: add ERC2771Context and a MinimalForwarder for meta-transactions. (#2508)
• Overall reorganization of the contract folder to improve clarity and discoverability. (#2503)
• ERC20Capped: optimize gas usage by enforcing the check directly in _mint. (#2524)
• Rename UpgradeableProxy to ERC1967Proxy. (#2547)
• ERC777: optimize the gas costs of the constructor. (#2551)
• ERC721URIStorage: add a new extension that implements the _setTokenURI behavior as it was available in 3.4.0. (#2555)
• AccessControl: added ERC165 interface detection. (#2562)
• ERC1155: make uri public so overloading function can call it using super. (#2576)

v4.0.0-beta.0

A beta release for Solidity 0.8. Read the announcement in the forum.

v3.4.0

Read the full announcement in the blog or check out the changelog.

Security Fixes

• ERC777: fix potential reentrancy issues for custom extensions to ERC777. (#2483)

If you're using our implementation of ERC777 from version 3.3.0 or earlier, and you define a custom _beforeTokenTransfer function that writes to a storage variable, you may be vulnerable to a reentrancy attack. If you're affected and would like assistance please write to security@openzeppelin.com. Read more in the pull request.