Initializer functions that are invoked separate from contract creation (the most prominent example being minimal proxies) may be reentered if they make an untrusted non-view external call.
Once an initializer has finished running it can never be re-executed. However, an exception put in place to support multiple inheritance made reentrancy possible in the scenario described above, breaking the expectation that there is a single execution.
Note that upgradeable proxies are commonly initialized together with contract creation, where reentrancy is not feasible, so the impact of this issue is believed to be minor.
https://github.com/skalenetwork/ima-c4-audit/blob/main/package.json
Avoid untrusted external calls during initialization.
A fix is included in the version v4.4.1 of @openzeppelin/contracts and @openzeppelin/contracts-upgradeable.
https://github.com/OpenZeppelin/openzeppelin-contracts/security/advisories/GHSA-9c22-pwxw-p6hx
