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First Flight #39
Beginner FriendlySolidity
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Submission Details
Severity: high
Valid

Core invariants not enforced before authorizing contract upgrade

0xshield

Description

The graduateAndUpgrade() function in LevelOne.sol fails to enforce several protocol-critical invariants before authorizing a system upgrade. This omission introduces significant risks of protocol corruption, misaligned payment logic, and broken progression rules.

The function unconditionally calls _authorizeUpgrade() and proceeds with fund distribution — all without verifying:

  • if the school session has ended (i.e., sessionEnd is reached),

  • whether each student received the required 4 weekly reviews,

  • whether each student has met the cutOffScore to graduate,

  • and if payments occur after a valid time period (i.e., every 4 weeks).

These checks are foundational to the protocol’s integrity and were explicitly documented as invariants.

function graduateAndUpgrade(address _levelTwo, bytes memory) public onlyPrincipal {
if (_levelTwo == address(0)) {
revert HH__ZeroAddress();
}
​
uint256 totalTeachers = listOfTeachers.length;
uint256 payPerTeacher = (bursary * TEACHER_WAGE) / PRECISION;
uint256 principalPay = (bursary * PRINCIPAL_WAGE) / PRECISION;
​
_authorizeUpgrade(_levelTwo); // ❌ Upgrade authorized without checking any invariant
​
for (uint256 n = 0; n < totalTeachers; n++) {
usdc.safeTransfer(listOfTeachers[n], payPerTeacher); // ❌ Incorrect pay logic (see below)
}
​
usdc.safeTransfer(principal, principalPay);
}

Impact

This results in:

Time-based session integrity loss: upgrades can be triggered at any time, even during an active session. The sessionEnd is declared but never used to enforce session completion.
Invalid graduation: students may be upgraded without completing the required reviews or meeting the cutOffScore, completely bypassing the educational logic.
Upgrade misuse: Upgrades should be a reward mechanism after a validated session. Without these guards, malicious or negligent principals can skip progression logic and steal funds.

Recommended Mitigations

  • Require that block.timestamp >= sessionEnd before allowing upgrade.

  • Validate that all students have exactly 4 reviews.

  • Enforce cutOffScore for all students before graduation.

  • Emit an Upgraded(address) event to track the upgrade.

Severity: High

Component Reason
Impact: High Funds can be misused; logic broken.
Likelihood: High All checks are currently missing; easily exploitable by the principal.
Confidence: High Code review and invariants documentation confirm the issues.

Tools Used

  • Manual Review

Updates

Lead Judging Commences

yeahchibyke Lead Judge
6 months ago
yeahchibyke Lead Judge 6 months ago
Submission Judgement Published
Validated
Assigned finding tags:

cut-off criteria not applied

All students are graduated when the graduation function is called as the cut-off criteria is not applied.

can graduate without session end

`graduateAndUpgrade()` can be called successfully even when the school session has not ended

no event

Event not emitted

yeahchibyke Lead Judge 6 months ago
Submission Judgement Published
Validated
Assigned finding tags:

cut-off criteria not applied

All students are graduated when the graduation function is called as the cut-off criteria is not applied.

can graduate without session end

`graduateAndUpgrade()` can be called successfully even when the school session has not ended

no event

Event not emitted

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