Check-effect-interaction pattern violation - High Severity!

[olahfemi]

Description
A reentrancy attack can occur when the contract creates a function that makes an external call to another untrusted contract before resolving any effects. If the attacker can control the untrusted contract, they can make a recursive call back to the original function, repeating interactions that would have otherwise not run after the external call resolved the effects.

Context:
cerificate.sol SOLC 96-98

Recommendation
We recommend using the Checks-Effects-Interactions Pattern to avoid the risk of calling unknown contracts to prevent reentrancy attack.