aBNBc

The decentralized-finance protocol said it is working with exchanges to immediately halt trading of its BNB staking rewards token, aBNBc.

BNB Chain-based decentralized finance (DeFi) protocol Ankr has confirmed it has been hit by a multi-million dollar exploit on Dec. 1.

The attack appeared to be first discovered by on-chain security analyst PeckShield at approximately 12:35 am UTC on Dec. 2. 

Within an hour of the attack, Ankr confirmed on Twitter that the aBNB token has been exploited and that they’re working with exchanges to immediately halt trading of the compromised token.

Our aBNB token has been exploited, and we are currently working with exchanges to immediately halt trading.

— Ankr (@ankr) December 2, 2022

The attacker was purportedly able to mint 20 trillion Ankr Reward Bearing Staked BNB (aBNBc), a reward-bearing token for BNB staked on the protocol.

According to a Twitter post from on-chain analysis firm Lookonchain, the exploiter has since used services such as Uniswap, Tornado Cash, and various bridges to swap and obfuscate the funds in order to gain around $5 million worth of USD Coin (USDC).

It also added in a following post that “all underlying assets on Ankr Staking are safe at this time, and all infrastructure services are unaffected.”

Seems that @ankr got hacked an hour ago!

The exploiter minted 20T aBNBc and dumped it on #PancakeSwap.

At present, the exploiter have successfully exchanged more than 5 million $USDC.https://t.co/hF1tgNYw0t pic.twitter.com/XIPjBi6wvs

— Lookonchain (@lookonchain) December 2, 2022

In comments to Cointelegraph about the attack, blockchain security firm Beosin suggested the exploit was likely the result of vulnerabilities in the smart contract code combined with compromised private keys, which may have come from a technical upgrade by the Ankr team about 12 hours ago.

Beosin also noted that the mass minting episode caused the price of aBNBc to fall 99.5% from $303.89 to $1.53 in a matter of hours, according to data from CoinMarketCap.

@ankr has been exploited. $aBNBc has dropped -99.5%.
The hacker minted tons of $aBNBc and made a profit of 5,500 BNB (~$1.6 million)
The deployer changed the implementation contract to the vulnerable contract address before the attack (possibly due to private key compromise). pic.twitter.com/GJheXh0oDp

— Beosin Alert (@BeosinAlert) December 2, 2022

“It is possible that the deployer’s private key was exposed in this upgrade, leading to an attacker using deployer privileges to modify the contract,” a Beosin spokesperson told Cointelegraph.

In a Dec. 2 Twitter post, crypto exchange Binance also confirmed its team is engaged with relevant parties to investigate the matter further, adding that Binance's user funds are not at risk.

We are aware of the attack targeting @ankr's aBNBc token. Our team is engaged with the relevant parties and @BNBCHAIN to investigate further.

This is not an attack against #Binance, and your funds are SAFU on our exchange. This thread will be updated should there be any updates.

— Binance (@binance) December 2, 2022

Cointelegraph contacted Ankr when the exploit was first discovered but did not receive an immediate response.