Upbit and Bithumb Put SAND Under Caution After Bridge Security Incident

Highlights:

• Upbit and Bithumb placed SAND under investment caution after a recent cross-chain bridge security incident.
• The Sandbox said attackers minted unbacked SAND on Base and BNB Smart Chain before bridging was disabled.
• Both exchanges continue reviewing SAND, while Bithumb plans another assessment between September 28 and October 2.

South Korean crypto exchanges Upbit and Bithumb have placed The Sandbox (SAND) under an investment caution designation after a recent security incident involving the token’s cross-chain bridge. Both exchanges announced the decision on August 24. The move came two days after unusual SAND minting activity raised security concerns. Upbit said it placed SAND under caution while it reviews the issue. Bithumb also took the same step and kept SAND deposits and withdrawals suspended. 

The exchanges have not delisted SAND. However, the caution status shows that they still want more clarity about the incident and the steps taken by The Sandbox team.

Upbit and Bithumb Designate SAND as an Investment Caution Asset Over Unresolved Security Incidents

According to official announcements, South Korea’s largest crypto exchange Upbit and second-largest crypto exchange Bithumb designated The Sandbox (SAND) as an investment caution… pic.twitter.com/xw32pP7v7t

— Wu Blockchain (@WuBlockchain) August 24, 2026

How the SAND Security Issue Started

The issue first appeared on August 22. Bithumb suspended SAND deposits and withdrawals at 11:11 a.m. KST after detecting signs of a security problem. The exchange later warned users about abnormal SAND minting on the Base network.

The Sandbox later confirmed a problem with its cross-chain bridge on Base and BNB Smart Chain. According to the project, an attacker found a weakness in the bridge and used it to mint SAND that did not have matching tokens locked on Ethereum.

The Sandbox said:

“An attacker was able to mint unbacked SAND on Base and BSC. We have disabled bridging to and from both networks.”

The team then stopped bridge activity on Base and BNB Smart Chain. The Sandbox also said SAND on Ethereum and Polygon remained safe. It said the incident did not affect user wallets. The project added that the SAND locked on Ethereum to support legitimate bridged tokens remained intact.

According to The Sandbox, the incident affected less than 0.01% of the total SAND supply. The team also warned users not to trade SAND on Base or BNB Smart Chain while it worked on the issue.

Upbit and Bithumb Continue to Review SAND

The Sandbox says it contained the bridge problem, but Upbit and Bithumb still want more information before removing the warning. Bithumb said it placed SAND under caution because the security issue had not been fully identified or resolved from the exchange’s review point of view.

The exchange said:

“Security incidents such as hacking have occurred whose causes have not been identified or remedied.”

Upbit placed SAND/KRW and SAND/BTC under trading caution at 3:00 p.m. KST on August 24. The exchange said the security incident could put users at risk because its cause had not been fully identified or resolved. Upbit will review SAND until the fifth week of September, from September 28 to October 4. After that review, it may remove the caution status, extend the review period, or end trading support if the issue remains unresolved. 

Bithumb plans to review SAND again between September 28 and October 2. The exchange may remove the caution status if the issue is fully resolved. It may also extend the review period or take further action if concerns remain.