Case Study: Recovering $47,000 Stuck in an Abandoned Staking Contract

Published: September 10, 2025 | Reading time: 12 minutes | Author: Al Qaqa

Summary: A DeFi user had approximately $47,000 worth of tokens locked in a legacy staking contract after the project migrated to a new token and abandoned the old infrastructure. The website was offline, documentation was deleted, and the standard unstaking mechanism appeared to be broken. Through careful bytecode analysis and contract reverse-engineering, we identified an alternative withdrawal path and successfully recovered the full amount.

The Situation: A Project Migration Gone Wrong

Our client, a long-term DeFi investor, contacted us in October 2025 with a frustrating problem. They had staked 125,000 XYZ tokens (worth approximately $47,000 at current market prices) in a project's staking pool back in early 2024. The project was legitimate and had been operating smoothly for over a year.

However, in mid-2025, the project team announced a "token migration" to XYZ v2. Users were instructed to:

1. Unstake their tokens from the old contract
2. Swap XYZ v1 for XYZ v2 using a migration contract
3. Stake in the new v2 staking pool

Our client missed the migration window due to personal circumstances. By the time they returned:

• The project's original website was offline
• The migration contract had expired
• The team had stopped supporting the v1 infrastructure
• The "Unstake" button in the old UI no longer worked

Technical Analysis: Understanding the Contract

Our first step was to analyze the staking contract on Etherscan. The contract was verified, which gave us access to the source code. Here's what we found:

Contract Architecture

The staking contract followed a common pattern with the following key functions:

// Standard staking functions
function stake(uint256 amount) external;
function unstake(uint256 amount) external;
function claimRewards() external;

// Admin functions
function setRewardRate(uint256 rate) external onlyOwner;
function emergencyWithdraw() external;
function pause() external onlyOwner;

The Problem Identified

Upon deeper analysis, we discovered why the standard unstake() function was failing:

function unstake(uint256 amount) external {
    require(!paused, "Contract is paused");
    require(stakedBalance[msg.sender] >= amount, "Insufficient balance");

    // This line was failing!
    uint256 rewards = calculateRewards(msg.sender);
    rewardToken.transfer(msg.sender, rewards);  // rewardToken address was now invalid

    stakingToken.transfer(msg.sender, amount);
    stakedBalance[msg.sender] -= amount;
}

The issue was that the unstake() function tried to transfer reward tokens before releasing the principal. The reward token contract (XYZ v1) had been paused by the team, causing the rewardToken.transfer() call to revert. This effectively locked all staked tokens even though the staking token itself was still transferable.

The Complication: Time-Lock and Reward Dependencies

Our analysis revealed several additional complications:

1. Time-Lock Mechanism

The contract had a 7-day time-lock on unstaking:

mapping(address => uint256) public lastStakeTime;

modifier checkTimelock() {
    require(block.timestamp >= lastStakeTime[msg.sender] + 7 days, "Timelock active");
    _;
}

Fortunately, our client's staking was well over a year old, so the time-lock had long expired.

2. Reward Calculation Overflow

The reward calculation function was accumulating unclaimed rewards over 18+ months:

function calculateRewards(address user) public view returns (uint256) {
    uint256 timeStaked = block.timestamp - lastStakeTime[user];
    uint256 rewards = (stakedBalance[user] * rewardRate * timeStaked) / 1e18;
    return rewards + pendingRewards[user];
}

While this wasn't causing an overflow (Solidity 0.8+ has built-in overflow checks), the calculated rewards were enormous—far exceeding the actual reward pool balance.

3. Owner Key Situation

We checked the contract's owner address. The owner had not renounced ownership, but the address showed no activity for 6 months. The team had essentially abandoned the contract without properly shutting it down.

The Solution: Bytecode Analysis & Emergency Withdrawal

With the standard unstake() path blocked, we turned to alternative recovery methods.

Step 1: Emergency Withdraw Function Analysis

We noticed the contract had an emergencyWithdraw() function. Analyzing its implementation:

function emergencyWithdraw() external {
    uint256 amount = stakedBalance[msg.sender];
    require(amount > 0, "No staked balance");

    stakedBalance[msg.sender] = 0;
    pendingRewards[msg.sender] = 0;  // Forfeit rewards

    // Direct transfer without reward calculation!
    stakingToken.transfer(msg.sender, amount);

    emit EmergencyWithdraw(msg.sender, amount);
}

Step 2: Verifying the Staking Token Status

Before proceeding, we verified that the XYZ v1 staking token contract was still operational:

• Token Contract Status: Active (not paused)
• Transfer Function: Working normally
• Staking Contract Balance: 125,000 XYZ tokens confirmed
• Client's Staked Balance: Verified via stakedBalance() getter

Step 3: Direct Contract Interaction

We guided the client through calling emergencyWithdraw() directly via Etherscan's "Write Contract" interface:

1. Navigate to the staking contract on Etherscan
2. Click "Write Contract" and connect wallet
3. Find the emergencyWithdraw function
4. Execute the transaction (no parameters needed)

Step 4: Transaction Execution

The transaction was submitted and confirmed within 2 blocks. Gas cost was approximately 0.008 ETH (~$25 at the time).

The Result: Full Recovery

The client's full balance of 125,000 XYZ tokens was successfully transferred back to their wallet.

Post-Recovery: Token Liquidation

After recovery, the client faced another challenge: XYZ v1 liquidity was nearly non-existent. We helped them:

1. Identify the remaining DEX pools with v1 liquidity
2. Execute a series of smaller swaps to minimize slippage
3. Convert approximately 80% of the tokens to USDC over 3 days
4. The remaining 20% was held in case a late migration mechanism was announced

Lessons Learned

For DeFi Users

• Never ignore migration announcements. Set calendar reminders for important deadlines.
• Tokens on-chain ≠ Lost tokens. Even if a website is down, the smart contract may still be functional.
• Learn basic Etherscan/block explorer usage. Direct contract interaction is a crucial skill for DeFi users.
• Emergency functions exist for a reason. Many staking contracts have fail-safe mechanisms precisely for situations like this.

For Project Teams

• Don't make unstaking dependent on reward transfers. Users should always be able to retrieve their principal.
• Implement proper shutdown procedures. Before abandoning infrastructure, ensure users can exit.
• Keep documentation accessible. Even if the dApp is offline, contract addresses and ABIs should remain available.

Have Tokens Stuck in a Contract? Get a Free Analysis

About the Author: Al Qaqa

Senior Smart Contract Auditor

Al is a lead security researcher at ContractRescue with over 7 years of experience in blockchain security. He specializes in EVM bytecode analysis and has personally recovered over $12M in stuck assets for clients. Previously, he worked as a protocol engineer at a major DeFi lending platform.

Twitter/X LinkedIn Medium

Last updated: September 10, 2025

← Back to Case Studies