Root + Impact

Root Cause: Broad ^0.8.20 pragma and non-specific OpenZeppelin import -> Impact: Future compiler versions or updated dependencies can introduce breaking changes, subtle behavior shifts, and reduce code readability/maintainability.

Description

• Floating Pragma (^0.8.20): Allows compilation with any 0.8.x or newer (but not including) 0.9.0 compiler. Future >0.8.20 releases could introduce subtle or breaking changes (new compiler optimizations or behavioral adjustments) that alter contract behavior.

• Unnamed Import: Importing OpenZeppelin’s Ownable in a traditional way (import "@openzeppelin/contracts/access/Ownable.sol";) without specifying a named import is considered poor practice.

At the top of Game.sol:

Risk

Likelihood: Low

• Together, these practices create a brittle foundation: redeployments, CI builds, or dependency installs at different times may yield different bytecode, causing non-deterministic behavior and harder audits.

Impact: Low (but can be an explosive in UUPs and ~ patterns)

• Non-Deterministic Builds: Different developers or CI runs may produce different artifacts, complicating reproducible deployments.

• Unexpected Behavior: Future compiler updates can silently alter logic, potentially introducing security regressions.

• Audit Fragility: Audits performed against one set of dependencies may not cover changes introduced later, invalidating security guarantees.

• Maintenance Overhead: Debugging subtle shifts between compiler/library versions consumes time and increases risk of oversight.

Tools Used:

• Foundry Test Suite

• Chat-GPT AI Assistance (Report Grammar Check & Improvements)

• Manual Review

Proof of Concept

Scenario:

Compiler Change: The Solidity team introduces a new built-in compiler check in v0.8.21 that modifies how empty fallback functions are treated. Suddenly, gameNotEnded modifier logic behaves unexpectedly under ^0.8.20. (not sure)
Library Update: In dev phase Upgrading OpenZeppelin from v4.8.0 to v4.9.0 changes Ownable’s transferOwnership event signature. Off-chain scripts listening for OwnershipTransferred events fail, disrupting admin workflows.

Recommended Mitigation

Pin Pragma to Exact Version

```solidity

• pragma solidity ^0.8.20;

• pragma solidity 0.8.20;

  ​

  -ensures all compilations use the same compiler release.

  ​

Use named Imports with Specific Versions

```solidity

• import "@openzeppelin/contracts/access/Ownable.sol";

• import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol@4.8.0";

  ​

  -ensures the exact version of `Ownable` is used, preventing unexpected changes.