OpenZeppelin Confidential Contracts `VestingWalletConfidential`: a malicious ERC-7984…

Summary

### Impact Two locations consume an encrypted handle returned by an untrusted external party and use it without verifying that the party is ACL-authorized on it. #### `VestingWalletConfidential` Malicious users can call `release` with a malicious token. This token could return an alternative handle on `confidentialBalanceOf`, which represents the balance of the vesting wallet on an alternative ERC-7984 token (or any other handle that the vesting wallet has access to). The vesting wallet does not check that the token has ACL access and grants access to a new handle derived from the returned handle. Effectively, this bug allows a malicious user to gain information about any private `euint64` handle that the vesting wallet has access to via a malicious ERC-7984 token. There is no loss of funds. #### ERC7984 On a transfer with callback, `ERC7984` uses the `ebool` returned by the recipient's `IERC7984Receiver.onConfidentialTransferReceived` to drive the refund logic, without checking that the recipient has ACL access to it. A malicious recipient can return any `ebool` the token has access to and recover its plaintext from the refund result, which the token grants the caller access to. The leak is limited to `ebool` handles (the value is only used as an `FHE.select` condition), and there is no loss of funds. ### Patches Both issues were fixed in the same patch releases: v0.5.2, v0.4.2, v0.3.2 - `VestingWalletConfidential`: 93e75ceed2b9648f53f9d133f431064353456805 (#423). - `ERC7984` transfer callback: fe0863af2c9dce7614acce98720a913bf6a767a5 (#428), with follow-up ee47edf189ab681cebdad18bfb53dee541987be2 (#431) permitting an uninitialized returned handle.