PANews reported on May 20 that Threshold Network posted on X platform stating that on May 18 at 18:04 UTC+8, an attacker attempted to mint tBTC without depositing the underlying BTC but failed, resulting in no invalid tBTC and users' funds remaining secure. As a precaution, given the rising frequency of malicious activities across the crypto ecosystem, Optimistic Minting has been temporarily paused. Minting is now conducted through a sweeping mechanism, extending the minting time from approximately 1.5 hours to about 6-7 hours.

According to reports, tBTC's foundational security model is based on a decentralized network of signers holding the underlying Bitcoin and verifying each native minting through verifiable Bitcoin SPV proofs. Optimistic Minting employs a different trust model, where the Minter and Guardian, rather than SPV proofs, confirm deposits, with a minting time of about 1.5 hours.