How much was lost in the Blizzard hack?

The Blizzard hack resulted in $1.1M in losses on November 13, 2021.

What attack technique was used in the Blizzard exploit?

The Blizzard exploit utilized Other. Understanding this attack vector is critical for smart contract auditors and developers building secure DeFi protocols.

How can developers prevent similar smart contract attacks?

Preventing smart contract hacks requires a combination of secure coding practices, thorough security audits, and understanding common attack vectors like reentrancy, oracle manipulation, and access control flaws. Smart Contract Hacking (SCH) provides hands-on training to help developers and auditors identify and prevent vulnerabilities before deployment.

Blizzard Hack

TOTAL LOST $1.1M

Medium Nov 13, 2021 Other

Affected Chain 2021 Incident surface

Recovered - No recovery reported

All-Time Rank #813 By amount stolen

Protocol Type Yield Target category

Incident Overview

The insider attack was performed by 2 team members: front-end and back-end developers.

Developers had access to the key contracts as they were members of a multisignature account, which requires only 2 signs.

1. Whitehat reported found bug in the vault contracts to the Immunefi team

2. Whitehat received bug bounty and the core team of Blizzard asked the back-end developer to remove retired vaults, put 0 reward rate and disable deposits.

3. Front-end and back-end started testing new vaults:

https://snowtrace.io/tx/0xf66a695d…f3f48e

4. Back-end dev set the rewardMintRate to 50 BLIZZ per block

5. Developers exploited the harvesting issue:

https://snowtrace.io/tx/0xa7818cb8…4b0363

6. Front-end dev had removed the retired PNG-AVAX vaults from the website front.

7. Developers exploited a single USDC vault:

https://snowtrace.io/address/0xdb696940…49b64e#code

8. Developers dumped received tokens:

https://snowtrace.io/tx/0x7cd6c8c8…00e482

9. Attackers used Anyswap bridge to transfer funds on Ethereum, and then, on the Binance Smart Chain

https://snowtrace.io/tx/0x198c7303…111495

10. Stolen funds were deposited into Tornado Cash mixer at:

https://explorer.bitquery.io/bsc/txs/transfers?sender=0xbb2c0ef4…2ea965&currency=BNB&receiver=0x0d5550d5…859b17

The exploit is described in 3 steps:

- Modify the rewardRate, by calling setRewardMintRate(uint256 _rate) with the following parameter: 50000000000000000000

- Deposit any amount of USDC and wait until the desired amount of tokens has been minted

- Call claim() to transfer the rewards from the origin pool and additional minted token rewards from the aggregator to the beneficiary.

Incident Report

Protocol / Project Blizzard

Date of Incident November 13, 2021

Attack Technique Other

Classification Yield Aggregator

Primary Source View Post-Mortem

Protocol Information

Protocol Type Yield

Affected Token BLIZZ

Official Website www.blizzard.network/

Protocol Twitter/X @BlizzardAVAX

Team Anonymous

Source Code Unverified

Market Context at Time of Hack

Token Categories

BNB Chain Ecosystem

Protocol Links

GitHub

What the Attacker Needed to Succeed

Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.

Technical Knowledge Deep understanding of other and Solidity and EVM internals

Capital Required Seed capital to cover gas and initial position setup

On-Chain Access Ability to interact with smart contracts and deploy a custom exploit contract

Protocol Analysis Identification of the exploitable vulnerability in Blizzard's contract logic - root cause: yield aggregator

Execution Speed Precise transaction ordering and timing to exploit the vulnerability within a single atomic block

Obfuscation Plan A strategy to launder and move stolen funds - typically through mixers, cross-chain bridges, or decentralized DEX swaps to resist tracing

What Auditors Should Check

Could this have been caught in audit? Likely — with a thorough Other audit checklist and test coverage

If you're auditing a protocol with similar architecture to Blizzard, these are the critical security checks that could have prevented this incident (November 2021).

Verify all logic paths related to Other are guarded by proper access controls and input validation
Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs

Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.

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Sources & References

01
Source 1 https://medium.com/@blizzardavalanche/blizzard-exploit-a-post-mo…

Threat Assessment

Severity Level

MEDIUM

Attack Vector Other
Root Cause Yield Aggregator
Year 2021

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