---
description: Unprotected upgradeable initializer
---

## Unprotected initializer

**Severity**: `High`
**ID**: `unprotected-initializer`

Flags upgradeable contracts whose public or external initializer can still be called directly on an
implementation contract that exposes a destructive entry point.

### What it does

Reports initializer-like functions that:

- are public or external;
- are marked with `initializer` or `reinitializer`;
- write state directly or through an internal helper; and
- are in an implementation whose constructor does not call an inherited `_disableInitializers()`; and
- are in a contract with a public or external `delegatecall`, `callcode`, or `selfdestruct` path
  that is not restricted to proxy calls with `onlyProxy`.

### Why is this bad?

An attacker can initialize the implementation directly, take ownership, and invoke its destructive
entry point. Destroying or corrupting an implementation can disable every proxy that delegates to
it.

### Example

#### Bad

```solidity
contract Vault is Initializable {
    address public owner;

    function initialize(address owner_) public initializer {
        owner = owner_;
    }

    function execute(address target, bytes calldata data) external {
        (bool ok,) = target.delegatecall(data);
        require(ok);
    }
}
```

#### Good

```solidity
contract Vault is Initializable {
    address public owner;

    constructor() {
        _disableInitializers();
    }

    function initialize(address owner_) public initializer {
        owner = owner_;
    }
}
```

### Notes

The lint is intentionally local: it does not inspect deployment scripts to prove whether a proxy is
initialized atomically. It focuses on implementation contracts that remain directly initializable
and can reach code paths that may destroy or replace implementation state.

The `onlyProxy` exemption is a name-based heuristic for common UUPS implementations.
