Unchecked External Calls in smart contracts occur when a contract calls external contracts or addresses without validating input, handling return values, or controlling gas usage, enabling attackers to execute reentrancy attacks, steal funds, or manipulate contract state.

Remediation

• Use checks-effects-interactions pattern: update internal state before making external calls.
• Validate external addresses and restrict calls to known, trusted contracts when possible.
• Handle and check return values from external calls; do not assume success.
• Limit gas forwarded to external calls to prevent unexpected execution or reentrancy.
• Consider using call, delegatecall, or send safely with proper error handling and guards.